Loving the comments here. Some of you wondering why people found THAC0 hard at all, and some of you expressing how they really disliked it. What’s clear is how divisive a mechanic it was, which isn’t good for any game. Really appreciate the comments. Thank you.
I find that the mechanic isn't hard. What's hard is to even remember what it is. It's such a forgettable formula that I feel I would have to relearn it every time I play. "Wait, do I add, or subtract? Which number is first? I forgot." It's like having to memorize the formula to convert Celsius to Fahrenheit. I know there's a 32 in it somewhere...
@@SergioLeRoux Player (level 2 Fighter) adds their d20 roll (rolled a 14) and their relevant modifier (Plus 1 Strength). Tell the DM that result (I got a 15). Players need not do anything else. The DM adds monster AC (Giant Rat - AC 7) to that result (for a 22) and that's the total. Is it equal or higher than the PC's THAC0 of 19? If so, they hit. Roll damage.
I preferred using THAC0 back in the day, as opposed to looking up stuff on charts. I simply explained THAC0 as being the number they need to hit and the target's AC as the modifier to their attack roll. Piece of cake. It's pretty much the same as using difficulty number + modifier method, with the exception that THAC0 is the difficulty number instead of the AC.
My group back in the day never seemed to struggle with THAC0, mainly because in hindsight, we seemed to look at it completely differently to practically everyone else at the time. We saw our THAC0 as the target we had to meet with our die roll, and the AC of the enemy was a number we'd add to our dice roll. So the weaker the armour, the bigger the bonus that was added to our die roll to achieve our THAC0 target, we never did any subtraction. For example, if our fighter's THAC0 was 18, and their opponent had an AC of 7, he'd roll his die and add 7, and if the total was 18 or better he'd succeeded, seemed pretty simple to us.
@@Coyote1911 I'll have to take a look at that system, I love looking at different interpretations of of the old-school rules. Thanks for giving it a mention!
Another simple tip is to add the AC to your roll and use thac0 as the target number - Chainmail is AC 5 so roll a d20+5 and try to score your thac0. Personally I like the tables for each weapon on a character sheet, but this works as well. I’ve heard it said that addition is typically easier to do in your head than subtraction.
the original to-hit tables were an artifact of Gygax's penchant for keeping game rules secret from players. and thac0 was an easy mathematical tool to fix that problem without changing armor class values and so on. my groups were full of nerdy guys who studied math and science, so we didn't have any problems with thac0. in fact we adopted it early, based on an article in Dragon magazine around 1982 or 83.
I have to say I agree with keeping rules secret from the player. In my opinion Rules Lawyers drag the game down. Even if I expressly tell them I'm using house rules. They have to quibble. And that stops things dead. So I'd rather just be trusted as the GM to have a decent understanding of the rules and be trusted to teach what is necessary to play the game.
Same here. Once we realized (it was also "sortof" mentioned in the original DMG if in one little footnote back in 79) it was so much easier than dealing/looking up hit tables.
@@DoctorEviloply I feel like rules lawyers became a think really after 3e. Not as much in the 2nd Edition era, and by then we had rules pretty much available to players, but we still had the concept that they were just guidelines. Even early 3e had a "rule 0" that superceded all rules, and it wasn't until 3.5 that that stopped being as much a thing. And thats when rules lawyers really came out of the woodwork.
I don't let my players know the AC I just ask them what they rolled + mod and tell them if they hit. That way it doesn't matter if they understand THAC0 or not.
This is pretty much how we did it. Then we would figure out the enemy AC after a few hits and misses anyway. I think the players shouldn't know or just be given the armor class of their opponent. A big nasty looking opponent could be a pushover and a scrawny looking one could be deadly. Just roll, add your modifiers and tell the DM. Keep the mystery alive 😂
@@MarkGoldfine yeah I mean some players can figure out the AC but with descending I find less put in the effort which I see as a feature. Also I generally don't want my players thinking of the game in terms of pure numbers or knowing the stat block I find it makes them do what I call bad meta gaming. This is also why I try to never say the name of a monster so for example "you see a small 2ft tall creature that resembles a shaggy dog standing upright, it is wielding a dagger" instead of "you see a Kobold wielding a dagger" I know the second is more convenient but the former paints a better mental image, I learned that from playing Call of Cthulhu.
I have my players tell me what they rolled and what their THAC0 is. Over time, some players, especially the old school ones, will do the math for me and just tell me what AC they would have hit. But I never require them to.
@@singledad1313 Yeah it's really not as big of a deal as the people who don't like descending AC make it out to be. Honestly I use it as a filter for players if you get upset about THAC0 then you're probably going to complain about other things and generally be someone I don't want to play with.
I only recently got into old school D&D for Dark Sun, and I ended up having to convert a lot of it to ascending AC for new players. Although Roll20 seems to do all the busywork for us at the time. There are actual several failures of THAC0 in game design. First is having to look up a table, think of any board game where you need to look up a table, matrixes, or reference. This is usually a death nail of enjoyment of those games as the game halts to check something. Second there are mental gymnastics for negative numbers being good, which is counter to wanting positive numbers such as HP, Gold, XP, Magic Swords but not Armor. Even if the formula is in theory simple to calculate it runs counter intuitive to other game mechanics. Third requires knowing the Monster AC. There is a good argument that there are some monsters you wouldn't know the AC. Either their hide or magic items. For Thac0 to work you need to provide the number so the player knows what hits. Otherwise you the GM needs to add another layer of memorized stats to your bookkeeping. What makes this worse is that its a core mechanic, GMs will either need to put in the effort to remove which takes up GM time and mental resources. Or you need to force uncertain newer players to play with something that is obsolete as we have multiple better ways of doing attacks in RPGs. Even though compatible OSR systems that do remove Thac0, if you want to play the classic modules you still need to convert those and bring them up. TLDR; Thac0 is an example that not everything in the old school system is impure gold to be refined. The early game designers were fallible in their decisions. I've only heard old players lament nostalgia about it, I have never meet a new player who had other games look fondly at Thac0.
THAC0: THAC0 - Your Total Roll = Lowest AC hit. So after modifiers your total roll is 21 and you have THAC0 18, 18 - 21 = -3 AC. -3 AC and worse is hit by you. It wasn't that hard. Sure, OSE and D&D 3.x+ using ascending AC was easier, but THAC0 wasn't as hard as people said it was. Basic subtraction.
Especially when you consider how few attack bonuses you seem to get. You need some decent stats to gain a modifier and it seems magic items aren't quite handed out like candy. So it mostly boils down to what number you roll on a d20. THAC0 is a 15, all you got to do is roll a 15 or higher and you hit an AC of 0. If their AC is a 4, treat your THAC0 as 4 lower. Simple as. This is coming from a 25 year old who pretty much just started playing 2e.
@@slydoorkeeper4783 Facts. I mean, we usually didn't see +2 weapons until level 7 or more (outside of daggers, for some reason), so let's pretend you're a 5th level Fighter (THAC0 16) with 16 STR (+2 to hit) and have a +1 Sword. You roll the d20. You add 3. You subtract it from your THAC0 of 16. That's the best AC you hit. I get that it wasn't great, but it is NOT the Gordian Knot of gaming people make it out to be.
Good old THAC0. I remember high level play in 2E, with negative THAC0 and a massively negative AC creating cognitive dissonance. Just like anything, it made sense enough in the cold light of day, but at 3am, the wheels fell off and we were counting on our fingers.
The point of Thac0, regardless of if you call it that or an attack table/matrix, is to simply give you an easy to reference example of what numbers you need to role. The biggest problem I've found is that the majority of people trying to explain it immediately pull out the big charts and graphs, which scares off potential players. Just explain to your players that Thac0 is a target number they have to roll on a d20, which gets raised or lowered by the enemy's defenses.
I played 2E for the longest time. When 3.0 became a thing we kept playing 2nd. But took some things from 3. Like ascending armor class. But one player just could not manage to wrap his head around the conversion. So we kinda did a weird mix of both where I kept converting back and forth in my head. :P Overall I get THAC0, but do think that the new way is a lot easier to grok.
The reason why people get confused with thac0 is because when you start almost nothing will have AC 0 so right out of the gate you have a table that requires extra math to fully utilize. Also, people can forget what the system fully represents, and in misunderstanding what the system represents they can make mathematical mistakes. Simply put most people confuse AC from new and old editions and they forget when using thac0 that when AC goes up, chance to hit INCREASES because higher AC is a poorer value. When I did 2e YEARS ago, I had a cheat sheet for thac0, I kept thac10, thac5, thac0, thac-5, and thac-10. That way I could easily jump up or down by only a few points to note the to hit value for any given AC fairly swiftly. I don't think we ever got far so having the thac -10 was honestly pointless. But I was a 14 year old kid so, if I could get it that easily, how is it so many cannot?
I never used THAC0. I just recorded the values on the sheet, like you did. When I played a B/X D&D game a couple of years ago with, people seemed quite happy doing this. In particularly one player who found it difficult to do mental arithmetic, really liked this idea. And yes, I put the modified values on the character sheet!
Ah THAC0, even hearing it said makes me think nostalgic thoughts back to my old days of 2e. You're not wrong when you say its divisive. I've never had a problem with it, in some silly way THAC0 is what makes me love playing older D&D. I'm not a math guy, but to me THAC0 is pretty intuitive, and I never needed the charts to figure it out, but I have a couple friends who have endless trouble with it. They're not stupid people, but THAC0 just doesn't jell in their brains, to the point where they'll give up trying to figure out what their real number is and just say a number that sounds right. In 2e there was a descending chart somewhere that they had to constantly reference, but it didn't seem to help them much. Its been much easier for them in 3rd and 5th, just knowing you add say +7 to your roll simplifies things for people. Its definitely more straightforward. In 2e you tend to ask what ac did you hit, while in 3rd and 5th I just ask what's your total. For some people that makes things clearer and easier. If it was up to me though I'd probably still be using THAC0. Its so weirdly backward, but its also very satisfying for reasons I can't really describe.
Descending armor class made sense when you think of it as "Armor, First Class" and "Armor, Second Class" and so on, with 10th class being naked flesh or ordinary clothing. _Zero_ and _negative_ Armor Class ratings are what throw a wrench into this. So if I were to reimagine such a system, I'd say that Armor Class of 1 is the best possible protection you can benefit from regardless of any configuration of protective spells and armors. If it's completely mundane arms and armor, there's always _a chance_ of getting through. A zero would be "there's literally no chance to hit this with this weapon type", like physical weapons on a ghost.
After having played 5e with a lot of casuals, you'd be surprised at how hard it is to get people to even bother remembering their to-hit bonuses. The "do I hit?" question becomes no easier with these players than THACØ. For this reason, I've found it easier to use the White Box character sheet which just prints the to-hit table on the character sheet. Tell the players the target's AC and they more readily discern whether they hit.
This right here really shows how THAC0 was really just a scapegoat. The problem that "ascending armor class and rolling over" was meant to solve was never really "solved" by that solution. As others have pointed out, the description of use was problematic and people found better ways to use the tool. Now we rely on the DM or, let's be honest, a computer, to perform the calculation so we think we're doing better overall. But the problem is still there. It just changed its outfit. Anybody remember the combat calculator wheels?
I think the conceptual problem with THAC0 _and_ lookup tables is that they're both oriented the wrong way. That is, they're both presented with the AC of the target as a known value. Actual play, however, usually keeps the target's AC secret from the person rolling. That is, we roll not to see whether we hit AC 5 but whether we hit whatever the DM is hiding behind the screen. Yes, you can subtract your roll from your THAC0 to find the lowest AC that you hit, but that's not at all an intuitive result for 99% of humanity. And having to switch mid-stream from higher=better to lower=better still doesn't help at all. After all, we English speakers tend to equate "x or better" and "at least x". It's natural to say, "I hit at least AC 2," but defending AC makes this intuitive statement ambiguous. Does the player mean AC 2 or better, or does he mean AC 2 or worse? Inverting AC jumps both these hurdles. Not only does it mean that rolling higher equals hitting higher, it reorients things so that the result doesn't depend on knowing the target AC.
I think the main advantage of the 3.0+ way of ascending is that it unifies rolls a bit. Where higher is always better and you roll a D20 and add a thing, regardless of it's an attack, a skill check or a saving throw.
I LOVED old BASIC. The gritty aspect, and low hit points is exactly what is missing from 5e. But the one thing I'd flush and never look back if I were playing today is the decending AC and the tables. They suck, period. Of course it was "easy" to check the chart, of course, but it's just a stupid extra step. There is no pimping these tables. You see... just find this handy dandy table and determine that to hit AC 2 you just need to roll a 17 will always be a useless steps when you could just CALL that AC 17. Descending armor class was just one of those rules from wargaming that people just accepted as "it's they way we've always done it" without ever even thinking "why" one should do extra steps.
Gonna have me nightmares tonight. Cheers. Just being chased by a huge rolling d20, each face just says 'THAC0'. Like a fever dream Indiana Jones B-roll. Side note, it did take me a few to wrap the noggin' around it, but once you do, its pretty easy to manage. And practice always helps, and no practice is better than under pressure from an Owlbear's rage. Stay cool!
Yep, using the ThAC0 bar that was pretty much on every character sheet until 3e because even sheets from 2e had them and if they didn't you scribbled one in the blank spaces, we all did it at one point or another. However, you just need the ThAC0 but unlike trying to math out the specific AC you need to hit like in the ad&d example you gave, we just figured out which AC we hit and told the DM. Roll the d20, add the modifers. Subtract that number from the ThAC0 and that is the AC you hit. The DM will know and tell you if you failed or not. Your ThAC0 is 15 and you have a +2 modifer, you rolled a 10+2= 12. Now subtract that from the ThAC0 giving you a 3. You hit AC 3 so that AC 5 from the example got hit congrats roll damage. You didn't need to do anything but say which AC you did hit. Not that hard. As a grognard it was nice to scroll the comments and see so many people having already understood the way we did ThAC0 back in the day than has ever been given credit for. Perhaps ThAC0 hate is hasbro's attempt to steer people away from the better version? And people who never really wanted to play but just wanted the beer and snacks a reason to back out? We may never know haha.
Ezzakly! I have always enjoyed THAC0 as part of the REAL D&D experience. THAC0-adjusted d20 roll = AC hit. I was told by a friend and DM way back in the 1980's that the LOWER the AC, the LOWER the chances of getting injured. Conversely, the GREATER the AC, the GREATER the chance of getting injured. Simple.
I feel like people (myself included) need to spend a lot longer mentally subtracting numbers than adding them. This might be why descending armor class was such a mental burden and why THAC0 ended up frustrating players.
For me being dyslexic, northing was worse then the dreaded "zero". I always kept skipping 0 as a value and my attacks were off by one. Now that I have my trusty cell phn app. I am much braver to THAC0.
THACO is one of the hardest sells for folks I know in re: old editions. I think you’re right in that the simple little table was a better option for a lot of people.
You, or the DM, can just add the target's AC to your d20 attack roll (plus bonuses). If it meets or beats your THAC0 it's a hit. No need to subtract the AC from the THAC0 at all. The 1e way of having 5x 20s in a row confused things a bit, but 2e sorted that out. That's how we played it for 15 years anyway!!
In my day, we used to subtract the result of the d20 from our Thac0. The difference gave us the armor class that our characters would hit. For example, if I have a Thac0 of 18 and I roll a 15 on my d20, I know I have hit an armor class of 3.
I think descending AC is the weirdest hill to die on. If I'd play D&D I would take the book and cross out the descending armor classes and write in the ascending ones. Make the game more playable. Keep the fire not the ashes.
I adopted THAC0 early, since it was way easier for me as the GM rather than bother with to hit tables for the monsters. I could just quickly figure out what numbers I needed to roll to hit each PC from one number and their ACs. Also, it was easy enough to add the bonuses to the dice roll: if your THAC0 was say 15, and you had STR bonus +2, and you rolled a 14... 14+2 = 16, I hit AC -1, GM, is it enough?
I am glad to have scrolled the comments and see others who finally get it. It warms my grognard heart to see. Maybe there is hope for the younger generations.
But why would players need to figure out how THACO works? Why use tables for this? I prefer the method of "just roll the dice and dm tells you if you hit".
Thank you for your work. Personally, I only play with THACO, I feel more comfortable with it. And I know your channel is focused on BECMI. But for Halloween, a video on the Psi-Blast of Advanced Dungeons and Dragons 1st edition. It'll be fun. And especially on the possibilities of using these rules in BECMI. 🐙🧠🙂
THAC0 was just part of the game when I played it in the 90's. But it was always one of the more fiddly bits and you had to pay closer attention to it than was really warranted for a base mechanic that told you whether you could hit something or not. When I ran AD&D 2e for a few players who started with 3.x or 5e a few years ago I told them THAC0 was optional. I explained the concept then gave them each a printed chart mapping THAC0 to Base Attack and = 3e armor. It only takes 21 lines to do this (earlier versions stop at -10/30 AC for PCs and if the game went long enough for them to encounter something with armor beyond this I was confident they would be able to adjust by then). The OSR games i've seen seem to go the same route or just adopt Base Attack and ascending AC from 3e+ outright.
Dude, if the slow kid in remedial math in my 7th grade game could figure out THAC0, anyone can figure out THAC0. People just want something to complain about.
As a Moldvay Basic and then 1st Ed AD&D DM, I happily used THACO for my monsters' attacks, but since I never told my players the AC or HP of monsters, just whether they hit (per the table taped to my screen, and my notes of their stats etc) and the visible effects of damage they rolled, it never came up for us. Coming back to GMing D&D with 5th Ed, and with far less time and mental agility at my disposal, I can't say I missed To-Hit tables or descending AC one tiny bit. However, having recently played in an excellent BECMI game, I noticed that our DM took the exact same approach to the whole matter as I had in the '80s, aside from the occasional discouraging "you need a 16", which upped the tension.
I started with 1E. When 2E came out I got THAC0 and thought it was better then referring to the Attack Roll Table all the time. What I didn't know about at the time was the AC To Hit chart on Basic D&D character sheets. Never could understand why it wasn't carried over to AD&D...
I am dyslexic and hate math (mild discalclia) and used THACO to make my own attack matrix tables. I started with BECMI when I was 9 years old… so when 2nd Edition came out THACO threw me off… but … my best friends explained it to me and showed me how it worked. He is an engineer now, I am an artist. Eventually this was the only reason why I grasped algebra in 7th grade. Lol😅. If I could do it, clearly anyone can… what is required is a good explanation. Thank you for helping.
Loved hearing about this. Stuff like this can be taken for granted in the wider design. Thanks for being candid in your comment and being open about your experience. It’s appreciated.
Such a shame that THAC0 is seen as needing eradication, the big red cross out symbol makes things pretty clear from you. If it's of help to DM's - even as just a short-hand aide like Gary intended, then it has utility. But such is the way with rules development and player accessibility needing to be worked with. I like BOTH descending and ascending AC and am conversant enough to use THAC0 - to me this type of content can be mis-used to be deliberately divisive and exclusionary. (EDIT: As already proved by this very comment section :( ) Having said this, I would never impose a mechanic on players uncomfortable with it. I like OSE's approach to AC - making both of them an option to choose. But I will still love my BECMI rules. Even published content that embraces THACO in stat blocks. Page 108 in the Rules Cyclopedia talks about this and has a reasonably good explanation of it. I also have a soft spot for 1e and even 2e AD&D :) Cool video as always though.
THAC0 was so nice to use. One of the things I think 2e really got right. Still can’t understand what the problem was for people. We were just kids and that basic math was well within our grasp. If you didn’t want to do the math on the fly, it was a matter of a minute to write a simple one liner on your character sheet with the calculations.
I think the to hit table was from wargames. Especially when only d6 was used, the table allowed more results with attack strength vs defense. A table matrix gives more depth with less complexity.
My thoughts exactly. I'm a miniatures wargamer myself, so I can easily see the to-hit tables as something inherited from wargames rules, particularly considering Gary Gygax's previous career as a wargames rules designer.
It's not that the maths in hard but that its an acronym and multi step process that you might have to repeat half a dozen times on the fly. Where as a look up chart is the doing the hard part once at your leisure not mid game and just doing less math every time.
I never had an issue with THAC0, of course I also played 1st ed of Twilight 2000 by GDW, and the character creation system of that game was the very definition of clunky. Cool video :).
Thac0 is great for a DM to avoid large table of small print where you have to scan and your eyes could easy skip up or down a line. I included in all my stat blocks for this convenience, but I never ask players to use it -- just roll and tell me the results and I tell if they hit. It would be nice if they all learned just to better understand the game, but at this point I don't think everyone will.
It was easy and you are the first person aside from my groups I have ever seen get it. d20+mods-ThAC0=AC you hit. The DM will tell you the rest. So bloody simple.
Using thac0 is actually a lot simpler than having to check a table all the time and you do not even need to know the AC you have to hit. Just roll a d20, add all the pertinent attack roll modifiers, then subtract the result from your thac0. That's the AC you have hit. Announce it and the DM will tell you if you have hit your foe or not. You only need to write one number and a few specific modifiers on your sheet, not an entire array of tables. And the DM doesn't need to spoiler you your foe's stats. Also, using it this way the descending AC is ininfluent, since it is not involved in calculations. The DM can do the same for monsters. Modern games with ascending AC are only slightly simpler, since they do not require you to subtract anything. The result of your roll plus modifiers is already the AC you have hit. AC 0 in modern games is 20.
Great video and I agree on all point and to add video... The last third is the classic TT game issue of "Where to put the crunch" which yes as a player it's easy as you only need to mess with descending armor class once per level up weapon/spell get... But as the DM? Like to me the DM should be the one saying what the players need to hhit inn a system like this... So they have to reference the table at leastt once while adding the monsters and add the AC for all players to that monster stat block... Fortunately you should have their character sheets but still I would never try something onn the fly inn combat or any low prep suff... Which how I do itt in my game system is armor is just another bar of health that normally needs to be depleted sooner and some weapons bypass other do more damage to it... But the to hit in combat unless the GM says other wise is based soly on the weapon and like a wargame you roll each dice a see they hit or not if that do they do damage and you might be able to do more damage if you artubies/ gear/ablities says you can... Yes complex to describe but easy and fast to play. Edit: Which where I want my crunch is on my the developer or on a homebrewer and keep it away from actual play as much as possible.
Great video. I have no dog in the fight, but have never nor will ever use THAC0. I have always disliked descending armor class and tables in combat. All of your points are great, but they are why I use other systems and games. I'll be referencing you and your work in my future videos (should I get around to producing them).
Never played tabletop, but I did play Baldurs Gate on PC when it was released and boy oh boy was this system confusing. Didn't help that I was a kid and English wasn't my native language, but I somehow managed to beat the game. Even seeing the word THAC0 gives me shivers, and not the good kind.
I realized a couple years ago that THAC0 and the old hit tables were really just poorly explained. They basically translate everything onto an attack roll modifier. Target number of 20, modified by class/level and enemy AC. Which, was then transformed into the base AC of 10 for an unarmored, average combatant. In both systems, that's true. But now, the AC is no longer a modifier, but a target number of its own. Ironically, I think the tables, while a handy shortcut, like you said, contributed to this mysticism around THAC0.
The other point was different weapons gave bonuses to different types of AC's. So a fighter could have a reason to switch to war hammer to hit that heavy plate armor. Back when player skill was paramount over class build and features. Not to mention a round was a minute, and weapon speeds were in segments of 6 seconds. That was shocking to me first time playing 5E. When I realized we were running around genetically at 6 second weapon speed segments, and not strategic minutes. It was an abstraction before. Where a war hammer took more segments to generate a hit in the round, but was more effective at hitting and with a much higher damage. Again, not to mention the fighters having better chances to hit than anyone. And different classes advanced at different rates, because experience point requirements were different. The thieves developed quicker, and we're better at what they did. And fighters slower, but still developed quicker at excelling at what they were designed to be good at. And The glass canon magic users slower with some spells taking a number of rounds to cast (making the magic user a target of the enemy and needed group tactics to protect), because -magic missile auto hit, and fireball massive area of effect and damage output...
The thing that I liked about THAC0 was the fact that fighters had a superior chance to hit difficult targets, while other classes had a worse chance. This meant that fighters were vastly superior in their bailiwick, i.e , marshal combat. The standard proficiency bonus of 5th edition levels the playing field to the detriment of the game. If all classes can be good at all things, why even have a class system in the first place? Back in the day, doing a bit of mental subtraction didn't feel difficult, mainly because our groups DM was a math nerd, and he'd work it out very quickly. I never understood why people found the concept difficult.
Good vid, Berserker 🤘 THAC0 is not complicated, never was, but when charts, etc are introduced, casual players eyes go wide and a lump forms in their throat. Knowing your THAC0 for your class at your level is enough. Roll a d20, add your modifiers and look at the little THAC0 bar at the bottom of your sheet. Or, roll, add modifiers and tell your DM what you got, and they will tell you if you hit or not (every self respecting DM running a game using THAC0 should have a THAC0 chart within quick reference reach). Initial fear of THAC0 is quickly overcome, and is easy to pick up, once you have played with it a little. That being said, I haven't played a D&D game using THACO, since the 90's 😅 Not for lack of want, though. Keep up the good work, Sir 🤘
All my saving throwing ive been needing to make these days are constitution checks for the lasting effects of sleep spells. THACO reminds me alot of the infamous Warhammer table top games's Weapon Skill Chart and Strenth vs toughness chart they made for their series of games, ive used them for decades and they are quite efficient, epecially once youve memorized them.
I got my start with 3rd edition, so what I've personally never understood about attack matrices or THAC0 is how the player is supposed to declare the result of their attack roll. Presumably an "old school" DM wouldn't divulge the enemy's AC, so does the player just say, for example, "I hit AC 1" and the DM then reveals whether or not it's a hit?
When I introduced THAC0 to 5e people, I simply said you don't need to do any maths, not even basic arithmetic. write the table according to the corresponding class you have. if you have bonus, move the result to your right, if it's penalty, move to the left. All you need is to count how many bonus/penalty you have, then look up the AC you hit. When I showed the table, everyone immediately understood. It would be better to have a similar scale on the AC on character sheet as well, make them circle their current AC, if there's bonus move to right and left for penalty. That leaves the only mental gymnastic which everyone still need to realize when I report I hit an AC number, is that if it's lower than your armor it means I hit not miss.
THAC0 seems fine to me tbh. Instead of having proficiency bonuses like in 5e it has a more personalized way to calculate the to-hit modifier that you get from your class. It reminds me of the to hit bonuses 3.5e characters got from their classes.
An even simpler solution, and the one my own table has used, is to let the DM tell you what your PC needs to hit a particular foe. Give the DM your THAC0 and he/she can work out what you need to hit and tell the player that number. Players don't need to know the AC of their foes (but will work that out in time) and the DM does all the heavy lifting. If the DM can't work out the numbers then they shouldn't be a DM.
I never got that. Ok, I suppose that a few people might game the system by knowing the exact number. On the other hand, you as an actual character would know how hard it would be to hit a person, once you had started a combat. If you started a combat, and knew that the AC was -8, I as a player would try to get away in the same way that the character would realise that all their attacks were being blocked, and combat was hopeless.
@@markbertenshaw3977 It often doesn't matter anyway. If a given character misses with a 13 and then later hits with a 14, the DM has effectively told everyone the target's AC and might as well have just done so from the start.
@@willmistrettaNo. The mystery and discovery is a way to make D&D realistic and more enjoyable for many people, like myself. It’s like the difference between seeing the entire dungeon map at the start of an exploration, or gradually discovering it (& mapping it) as we explore.
I've never had any sympathy for THAC0, and zero nostalgia for it. For one, my dyscalculia made it a nightmare for everyone. Second, I mean, it's such grognard bs, right? Complicated for the sake of being complicated. It's like that party everyone brags about going to: if you remember it fondly, you weren't there.
While clearly a divisive mechanic which some had difficulty with, personally I found THAC0 vastly quicker and more convenient than attack grids and combat wheels. I don't recall ever issues with players not understanding its use, or having to explain it multiple times. No shade thrown on those who found it troublesome or simply disliked it, but it's as simple as "roll, subtract, go" and frankly, I never understand the reasons it is so reviled.
Another good video. I guess I'm in the camp of not understanding what is so hard about THACO. Better than AC 0 you add and if it went the other way you subtract. I guess if you want to make it easy then just make your self a to hit chart for your PC and then just adjust for ability scores and magic items ( the +1 sword ). Once again a good video representing OSR gaming and BECM.
AC isn't always known with certainty to the players, or at least for the first few rounds. So our table convention is to subtract the modified die roll from the THAC0. Then they can say "I hit AC (N)." If that bar is too high, then Hero Quest might be a better fit, a game everyone can enjoy, myself included!
I liked Thac0, it made sense to me when I first played. But I had friends who never understood their attacks until 3rd edition came out. As I write my homebrew rules for an old school game now I am using ascending AC and attack bonuses. It is so players can more easily understand the game.
I've never played properly played any edition of D&D, but I understand that the concept of a "lower" AC being better throws players off who have been trained to see higher numbers as better. I've seen alternative ascending AC offered up, but I've never understood why players wouldn't just change the minus in descending AC to a plus, and adding a minus to the "high" ACs. The intention being that the AC is added or subtracted to the attacker's THAC0 to generate the attacker's target number to hit. So I would change it from; 2 / 1 / 0 / -1 / -2 Into something like; -2 / -1 / 0 / +1 / +2 I assume that would be an easy fix, unless I'm mistaken.
Good morning, sir. You have commented about retro clones games with ascending armour class system. One of those i recently know is Castles & Crusades. I would really appreciate your opinion about that game. Thanks a lot for your work.
Playing RC now, having come from OSE, so we just convert THAC0/Descending AC to To Hit bonus/Ascending AC. It’s easy. For BX/BECMI/RC: 19 - Descending AC = Ascending AC For Characters: 19 - THAC0 = To Hit bonus For Monsters: If HD has a plus, To Hit bonus equals HD; if HD doesn’t have a plus, To Hit bonus equals HD-1. Players still reference the same THAC0 for their class/level, and still add ability/magic mods as normal. Convert away!
I like THAC0. While I agree it didn't improve much for BECMI I think it was an improvement over the AD&D attack tables. Since those were located in the DMG we used to have the player's announce their adjusted roll, then the DM would have to look up whether the player hit in the DMG and let the player know. THAC0 made 2E combat a bit faster and less onerous for the DM.
I really feel like wotc, and fans of 3e trying to get new players or ad&d players to join up, that REALLY drummed up the thaco=bad narrative. It was a dramatic change and everyone was trying to get those on the fence on board with the new ways. IMO Descending AC was the only problem with the old system, and thac0 took the fall for it. E.G. For all the 5e players who complain that you shouldnt have to subtract to figure out your hit roll (thac0), I ask them how many times they've done the following: "so the enemy has a 16 AC? Let's see, my total bonuses are +7, so I need to roll a... 9 to hit!" Subtracting to figure out what to hit is apparently fine in d20 systems, but not fine with thac0.
Hey BECMI Berserker. I really enjoy your videos but this one still had me scratching my head a bit. I’ve not played Descending Armour Class before as I started in 3E and later, so I was hoping that this video could clear it up for me. I think part of the problem for me is the with the ‘AC’ in the acronym I keep on thinking of the defence rather than just calling, as you called it briefly, the “Attack Roll”. So THAc0 is the attack roll & is how hard you hit. If I’m attacking a Yeti with an AC of 6, and my Attack Roll is 18, then I’ve got to roll an attack of 12 or higher to hit. (That being 18 - 6 = 12) If I’m rolling against Eclavdra, the Drow High Priestess who has an AC of -6, then I’ve got the impossible task of trying to roll a 24 to hit off a d20. (That being 18 - (-6) = 18 + 6= 24). It is times like that I wished I played DCC so I can use the d24 and d30 dice! Have I got all this right?
I think so, assuming that what you’re referring to as the Attack Roll value being what you need to hit an AC of 0. Thanks for watching my videos by the way.
oh also, in a competently-run 2e game, players shouldve never had to deal with thac0 anyway - all the players have to do is roll, add their mods, then the DM checks the thac0 and AC to determine whether they hit. Thats how I run my 2e campaign, and thats how I ran my intro adventure the last convention I went to. My players, all coming from 3e and 5e, all had an overall positive "I wonder what all the thac0 fuss was about?" impression from the sessions
THAC0 is an elegant system but Zeb Cook messed up when he explained it with subtraction. Human beings in general find addition easier than subtraction (and more pleasing cause number go up make brain release the happy drugs). The 1991 Black Box edition of the Basic rules explained it completely by using addition and have the THAC0 be the Target Number. If they explained it that way and called it something easier like "Attack Number" or "Hit Number", it would be more well-liked.
If you really don't like THAC0, OSE has a table to convert THAC0 to Attack Bonus/ascending armour class. It's pretty simple and doesn't really impact anything outside of it.
D20 + (modifiers including target AC) vs thac0 Or D20 + (modifiers including ones added in later editions) vs AC It's no more or less complicated I played the game back in the day and I remember a lot of people explaining it completely incorrectly and trying to reverse engineer it so that AC ended up being the target number. But it's just a simple as later editions. Fear over thac0 is so weird.
Finally, some that explains THAC0 in a way I can understand! I had already figured out the To Hit Table's about a month ago but was still struggling with THAC0, thank you for showing how to finally solve this puzzle.
Guys, here's how easy THACO is. Ready? Player: "My THACO is 17" DM: "Roll to attack" Player: (rolling d20) "12, I hit AC 5" DM: (Looking at goblins' AC 6) "That's a hit. Roll damage" Any questions?
back in 2e days we used to do this: 1. roll dice and add any mods from str/dex and magic weapon mod 2. substract the roll from Thac0 3. declare the AC hit to the DM 4. DM would say you hit or not. This created mystery tension and good anger. Love Thac0. Modern AC is boring
I never really had a problem with THAC0 - it made sense as a quick shorthand for the tables, with AC0 being in the middle of the AC 'continuum' (ok, not a real continuum). I used to calculate my bonuses and then write down that THAC0, so an atatck was a mere 'whats the AC' question (just like 5e, now). That said, my experience is not everyones, and people can now choose which they like - and thats a good thing!
I run a weekly BECMI D&D game that started during the pandemic. The player's ages are 8, 10, and three 12 year olds. They were 3 years younger when it started (except for the 8 year old, who was 6 when he stated. He plays an Ogre so it works with his little kid mentality. But none of them have a problem with subtracting AC from Thac0, not even the Ogre. What many people miss, is that Thac0 is what makes combat at higher levels work in BECMI, and its absence is what makes high level combat in d20 so meh.
This is all so silly. THACO is so simple and it's so helpful as a DM. Essentially, with the ascending Armor classes the designers simply pulled the bonus PCs get out of the table and made it a plus that they add to their dice roll. Then they roll against the higher number. Descending Armor Class bakes that bonus into the table, so you simply subtract your foe's AC from the THACO number on the table. It's one number with the attack bonus baked into it. Honestly they are 6 of one or a half-dozen of the other. Either way it's the same! I personally prefer Descending AC/THACO because it is simpler to me. I have my THACO, all I need is my foe's AC and I know the to hit number. I run an AD&D Fighter named Cei. He uses a two-handed sword +1, has 17 Strength (+1 to hit), and is a 5th Level Fighter. According to the newer OSRIC book page 14 he has a basic THACO of 16. So I load that number up a bit by subtracting my other bonus' from that: Sword -1, Str -1. That gives me an overall THACO of 14. That's all I need to write on my character sheet- THACO 14. Why a 14? Because that's literally what I need to roll on my D20 to hit AC 0. From there all I do is subtract positive ACs or add negative ACs and I get exactly the # I need. It's isn't tough math. Let's say that I need to hit a well protected Orc lord who has an AC 3. I simply subtract that 3 from my THACO of 14- I need a 11 on my die roll. With THACO I've done all of my math work BEFORE the game and not DURING the game that most people do with ascending AC (which speeds up the GAME!). Now all I need to do is just subtract a foe's AC from my THACO and I'm good to go. If the DM tosses in modifiers then I just account for them when I roll. Let's say he's stunned, so I got a +2 to hit. Easy to do. I just tick off another two from my to hit. My 11 now becomes a 9. For a lot of people it's confusing as you're reversing everything because the original attack bonus is baked into the to hit chart. For example, a 1st Level Fighter has a THACO of 20. That's a +0 attack bonus while my Cei, 5th Level, has a basic THACO of 16 which is four less than the 20. That means that Cei has an attack bonus of +4 in the modern system (modern fighters get a +3, but they are better off as they get another attack at 5th... AD&D has to wait until 6th level and even them is just 3 attacks every two rounds... :( ). Anyway, modern D&D just strips the attack bonus you get at higher levels out of the attack chart and puts them facing the players rather than bakes them into the attack chart and hides them from players (DM faced). At the end of the day, it's literally the SAME THING math wise. However I do get why many people prefer ascending ACs. The math appears to be simpler because it's player facing.
Anybody ever subtract their d20 roll from their THAC0 to see what AC they hit? You know, for those DMs that kept AC of monsters a secret. THAC0 18 minus roll of 13 means you hit AC 5 or worse.
This can be so much easier. The players only need to roll a d20 and add the relevant modifier. Give that result to the DM. The DM adds the enemy's AC to that and compares to the player's THAC0. Is the total higher than their THAC0? If so, they hit. A level 4 Fighter rolls a 12 and adds +2 for high STR. 14. The goblin that they hit has AC 6, so the DM adds that. Total of 20. 20 is equal or higher than THAC0 17, so the fighter hits the goblin. Roll damage. This makes it virtually the same as adding up bonuses and whatnot in 5e.
Loving the comments here. Some of you wondering why people found THAC0 hard at all, and some of you expressing how they really disliked it. What’s clear is how divisive a mechanic it was, which isn’t good for any game.
Really appreciate the comments. Thank you.
I find that the mechanic isn't hard. What's hard is to even remember what it is. It's such a forgettable formula that I feel I would have to relearn it every time I play.
"Wait, do I add, or subtract? Which number is first? I forgot."
It's like having to memorize the formula to convert Celsius to Fahrenheit. I know there's a 32 in it somewhere...
@@SergioLeRoux "Subtract AC from Thac0"
@@SergioLeRoux Player (level 2 Fighter) adds their d20 roll (rolled a 14) and their relevant modifier (Plus 1 Strength). Tell the DM that result (I got a 15). Players need not do anything else. The DM adds monster AC (Giant Rat - AC 7) to that result (for a 22) and that's the total. Is it equal or higher than the PC's THAC0 of 19? If so, they hit. Roll damage.
I preferred using THAC0 back in the day, as opposed to looking up stuff on charts. I simply explained THAC0 as being the number they need to hit and the target's AC as the modifier to their attack roll. Piece of cake. It's pretty much the same as using difficulty number + modifier method, with the exception that THAC0 is the difficulty number instead of the AC.
My group back in the day never seemed to struggle with THAC0, mainly because in hindsight, we seemed to look at it completely differently to practically everyone else at the time. We saw our THAC0 as the target we had to meet with our die roll, and the AC of the enemy was a number we'd add to our dice roll. So the weaker the armour, the bigger the bonus that was added to our die roll to achieve our THAC0 target, we never did any subtraction. For example, if our fighter's THAC0 was 18, and their opponent had an AC of 7, he'd roll his die and add 7, and if the total was 18 or better he'd succeeded, seemed pretty simple to us.
That's a really nice way of playing it!
@@Coyote1911 I'll have to take a look at that system, I love looking at different interpretations of of the old-school rules. Thanks for giving it a mention!
This method of viewing it comes from the AD&D Dragon Quest board game
I still play 2e
Thaco speeds up combat
Excellent. Thank you very much.
Another simple tip is to add the AC to your roll and use thac0 as the target number - Chainmail is AC 5 so roll a d20+5 and try to score your thac0. Personally I like the tables for each weapon on a character sheet, but this works as well. I’ve heard it said that addition is typically easier to do in your head than subtraction.
Yes. Modern system just swapped two numbers around. They are literally identical besides that.
the original to-hit tables were an artifact of Gygax's penchant for keeping game rules secret from players. and thac0 was an easy mathematical tool to fix that problem without changing armor class values and so on. my groups were full of nerdy guys who studied math and science, so we didn't have any problems with thac0. in fact we adopted it early, based on an article in Dragon magazine around 1982 or 83.
I have to say I agree with keeping rules secret from the player. In my opinion Rules Lawyers drag the game down. Even if I expressly tell them I'm using house rules. They have to quibble. And that stops things dead. So I'd rather just be trusted as the GM to have a decent understanding of the rules and be trusted to teach what is necessary to play the game.
Same here. Once we realized (it was also "sortof" mentioned in the original DMG if in one little footnote back in 79) it was so much easier than dealing/looking up hit tables.
@@DoctorEviloply I feel like rules lawyers became a think really after 3e. Not as much in the 2nd Edition era, and by then we had rules pretty much available to players, but we still had the concept that they were just guidelines. Even early 3e had a "rule 0" that superceded all rules, and it wasn't until 3.5 that that stopped being as much a thing. And thats when rules lawyers really came out of the woodwork.
Honestly, ascending AC makes so much more sense and converting to it is so easy that I’m embarrassed I didn’t think of it back in the day.
I think many of us are of the same thinking. How did we miss it??
I don't let my players know the AC I just ask them what they rolled + mod and tell them if they hit. That way it doesn't matter if they understand THAC0 or not.
This is pretty much how we did it. Then we would figure out the enemy AC after a few hits and misses anyway.
I think the players shouldn't know or just be given the armor class of their opponent.
A big nasty looking opponent could be a pushover and a scrawny looking one could be deadly.
Just roll, add your modifiers and tell the DM. Keep the mystery alive 😂
@@MarkGoldfine yeah I mean some players can figure out the AC but with descending I find less put in the effort which I see as a feature.
Also I generally don't want my players thinking of the game in terms of pure numbers or knowing the stat block I find it makes them do what I call bad meta gaming. This is also why I try to never say the name of a monster so for example "you see a small 2ft tall creature that resembles a shaggy dog standing upright, it is wielding a dagger" instead of "you see a Kobold wielding a dagger" I know the second is more convenient but the former paints a better mental image, I learned that from playing Call of Cthulhu.
@@BX-advocate Exactly this 👍
I have my players tell me what they rolled and what their THAC0 is. Over time, some players, especially the old school ones, will do the math for me and just tell me what AC they would have hit. But I never require them to.
@@singledad1313 Yeah it's really not as big of a deal as the people who don't like descending AC make it out to be. Honestly I use it as a filter for players if you get upset about THAC0 then you're probably going to complain about other things and generally be someone I don't want to play with.
I only recently got into old school D&D for Dark Sun, and I ended up having to convert a lot of it to ascending AC for new players. Although Roll20 seems to do all the busywork for us at the time. There are actual several failures of THAC0 in game design.
First is having to look up a table, think of any board game where you need to look up a table, matrixes, or reference. This is usually a death nail of enjoyment of those games as the game halts to check something.
Second there are mental gymnastics for negative numbers being good, which is counter to wanting positive numbers such as HP, Gold, XP, Magic Swords but not Armor. Even if the formula is in theory simple to calculate it runs counter intuitive to other game mechanics.
Third requires knowing the Monster AC. There is a good argument that there are some monsters you wouldn't know the AC. Either their hide or magic items. For Thac0 to work you need to provide the number so the player knows what hits. Otherwise you the GM needs to add another layer of memorized stats to your bookkeeping.
What makes this worse is that its a core mechanic, GMs will either need to put in the effort to remove which takes up GM time and mental resources. Or you need to force uncertain newer players to play with something that is obsolete as we have multiple better ways of doing attacks in RPGs. Even though compatible OSR systems that do remove Thac0, if you want to play the classic modules you still need to convert those and bring them up.
TLDR; Thac0 is an example that not everything in the old school system is impure gold to be refined. The early game designers were fallible in their decisions. I've only heard old players lament nostalgia about it, I have never meet a new player who had other games look fondly at Thac0.
The players do not need to know the target AC:
THAC0 - (d20 roll + modifiers) = The best AC you can hit.
THAC0: THAC0 - Your Total Roll = Lowest AC hit. So after modifiers your total roll is 21 and you have THAC0 18, 18 - 21 = -3 AC. -3 AC and worse is hit by you. It wasn't that hard. Sure, OSE and D&D 3.x+ using ascending AC was easier, but THAC0 wasn't as hard as people said it was. Basic subtraction.
Especially when you consider how few attack bonuses you seem to get. You need some decent stats to gain a modifier and it seems magic items aren't quite handed out like candy. So it mostly boils down to what number you roll on a d20. THAC0 is a 15, all you got to do is roll a 15 or higher and you hit an AC of 0. If their AC is a 4, treat your THAC0 as 4 lower. Simple as. This is coming from a 25 year old who pretty much just started playing 2e.
@@slydoorkeeper4783 Facts. I mean, we usually didn't see +2 weapons until level 7 or more (outside of daggers, for some reason), so let's pretend you're a 5th level Fighter (THAC0 16) with 16 STR (+2 to hit) and have a +1 Sword. You roll the d20. You add 3. You subtract it from your THAC0 of 16. That's the best AC you hit. I get that it wasn't great, but it is NOT the Gordian Knot of gaming people make it out to be.
Good old THAC0. I remember high level play in 2E, with negative THAC0 and a massively negative AC creating cognitive dissonance. Just like anything, it made sense enough in the cold light of day, but at 3am, the wheels fell off and we were counting on our fingers.
I love THACO - no time wasted looking up tables
The point of Thac0, regardless of if you call it that or an attack table/matrix, is to simply give you an easy to reference example of what numbers you need to role. The biggest problem I've found is that the majority of people trying to explain it immediately pull out the big charts and graphs, which scares off potential players.
Just explain to your players that Thac0 is a target number they have to roll on a d20, which gets raised or lowered by the enemy's defenses.
I played 2E for the longest time. When 3.0 became a thing we kept playing 2nd. But took some things from 3. Like ascending armor class. But one player just could not manage to wrap his head around the conversion. So we kinda did a weird mix of both where I kept converting back and forth in my head. :P
Overall I get THAC0, but do think that the new way is a lot easier to grok.
Didn't have any problem with Thac0 but my mathematically-challenged butt doesn't miss it either
Yeah I think i'll just stick with rolling to beat enemy's AC with some to-hit modifiers, thanks
The reason why people get confused with thac0 is because when you start almost nothing will have AC 0 so right out of the gate you have a table that requires extra math to fully utilize.
Also, people can forget what the system fully represents, and in misunderstanding what the system represents they can make mathematical mistakes.
Simply put most people confuse AC from new and old editions and they forget when using thac0 that when AC goes up, chance to hit INCREASES because higher AC is a poorer value.
When I did 2e YEARS ago, I had a cheat sheet for thac0, I kept thac10, thac5, thac0, thac-5, and thac-10.
That way I could easily jump up or down by only a few points to note the to hit value for any given AC fairly swiftly.
I don't think we ever got far so having the thac -10 was honestly pointless. But I was a 14 year old kid so, if I could get it that easily, how is it so many cannot?
I always thought of it as just looking at the same thing from a different angle; it's all about finding the target number.
Great video as always!
I never used THAC0. I just recorded the values on the sheet, like you did. When I played a B/X D&D game a couple of years ago with, people seemed quite happy doing this. In particularly one player who found it difficult to do mental arithmetic, really liked this idea. And yes, I put the modified values on the character sheet!
Ah THAC0, even hearing it said makes me think nostalgic thoughts back to my old days of 2e. You're not wrong when you say its divisive. I've never had a problem with it, in some silly way THAC0 is what makes me love playing older D&D.
I'm not a math guy, but to me THAC0 is pretty intuitive, and I never needed the charts to figure it out, but I have a couple friends who have endless trouble with it. They're not stupid people, but THAC0 just doesn't jell in their brains, to the point where they'll give up trying to figure out what their real number is and just say a number that sounds right. In 2e there was a descending chart somewhere that they had to constantly reference, but it didn't seem to help them much. Its been much easier for them in 3rd and 5th, just knowing you add say +7 to your roll simplifies things for people. Its definitely more straightforward. In 2e you tend to ask what ac did you hit, while in 3rd and 5th I just ask what's your total. For some people that makes things clearer and easier. If it was up to me though I'd probably still be using THAC0. Its so weirdly backward, but its also very satisfying for reasons I can't really describe.
Descending armor class made sense when you think of it as "Armor, First Class" and "Armor, Second Class" and so on, with 10th class being naked flesh or ordinary clothing. _Zero_ and _negative_ Armor Class ratings are what throw a wrench into this.
So if I were to reimagine such a system, I'd say that Armor Class of 1 is the best possible protection you can benefit from regardless of any configuration of protective spells and armors. If it's completely mundane arms and armor, there's always _a chance_ of getting through. A zero would be "there's literally no chance to hit this with this weapon type", like physical weapons on a ghost.
Original 1974 D&D had only Armour Classes 2 through 9. Not quite what you're looking for though.
I must say, I LOVE THAC0... no jokes :)
After having played 5e with a lot of casuals, you'd be surprised at how hard it is to get people to even bother remembering their to-hit bonuses. The "do I hit?" question becomes no easier with these players than THACØ. For this reason, I've found it easier to use the White Box character sheet which just prints the to-hit table on the character sheet. Tell the players the target's AC and they more readily discern whether they hit.
This right here really shows how THAC0 was really just a scapegoat. The problem that "ascending armor class and rolling over" was meant to solve was never really "solved" by that solution. As others have pointed out, the description of use was problematic and people found better ways to use the tool. Now we rely on the DM or, let's be honest, a computer, to perform the calculation so we think we're doing better overall. But the problem is still there. It just changed its outfit. Anybody remember the combat calculator wheels?
@@0ptikGhost I still have my combat calculator wheel! I don't use it though, never really did.
I think the conceptual problem with THAC0 _and_ lookup tables is that they're both oriented the wrong way. That is, they're both presented with the AC of the target as a known value. Actual play, however, usually keeps the target's AC secret from the person rolling. That is, we roll not to see whether we hit AC 5 but whether we hit whatever the DM is hiding behind the screen. Yes, you can subtract your roll from your THAC0 to find the lowest AC that you hit, but that's not at all an intuitive result for 99% of humanity.
And having to switch mid-stream from higher=better to lower=better still doesn't help at all. After all, we English speakers tend to equate "x or better" and "at least x". It's natural to say, "I hit at least AC 2," but defending AC makes this intuitive statement ambiguous. Does the player mean AC 2 or better, or does he mean AC 2 or worse?
Inverting AC jumps both these hurdles. Not only does it mean that rolling higher equals hitting higher, it reorients things so that the result doesn't depend on knowing the target AC.
I think the main advantage of the 3.0+ way of ascending is that it unifies rolls a bit. Where higher is always better and you roll a D20 and add a thing, regardless of it's an attack, a skill check or a saving throw.
I LOVED old BASIC. The gritty aspect, and low hit points is exactly what is missing from 5e. But the one thing I'd flush and never look back if I were playing today is the decending AC and the tables. They suck, period.
Of course it was "easy" to check the chart, of course, but it's just a stupid extra step.
There is no pimping these tables. You see... just find this handy dandy table and determine that to hit AC 2 you just need to roll a 17 will always be a useless steps when you could just CALL that AC 17.
Descending armor class was just one of those rules from wargaming that people just accepted as "it's they way we've always done it" without ever even thinking "why" one should do extra steps.
Gonna have me nightmares tonight. Cheers. Just being chased by a huge rolling d20, each face just says 'THAC0'. Like a fever dream Indiana Jones B-roll.
Side note, it did take me a few to wrap the noggin' around it, but once you do, its pretty easy to manage. And practice always helps, and no practice is better than under pressure from an Owlbear's rage. Stay cool!
Yep, using the ThAC0 bar that was pretty much on every character sheet until 3e because even sheets from 2e had them and if they didn't you scribbled one in the blank spaces, we all did it at one point or another. However, you just need the ThAC0 but unlike trying to math out the specific AC you need to hit like in the ad&d example you gave, we just figured out which AC we hit and told the DM. Roll the d20, add the modifers. Subtract that number from the ThAC0 and that is the AC you hit. The DM will know and tell you if you failed or not. Your ThAC0 is 15 and you have a +2 modifer, you rolled a 10+2= 12. Now subtract that from the ThAC0 giving you a 3. You hit AC 3 so that AC 5 from the example got hit congrats roll damage. You didn't need to do anything but say which AC you did hit. Not that hard.
As a grognard it was nice to scroll the comments and see so many people having already understood the way we did ThAC0 back in the day than has ever been given credit for. Perhaps ThAC0 hate is hasbro's attempt to steer people away from the better version? And people who never really wanted to play but just wanted the beer and snacks a reason to back out? We may never know haha.
Ezzakly!
I have always enjoyed THAC0 as part of the REAL D&D experience.
THAC0-adjusted d20 roll = AC hit.
I was told by a friend and DM way back in the 1980's that the LOWER the AC, the LOWER the chances of getting injured. Conversely, the GREATER the AC, the GREATER the chance of getting injured. Simple.
Honestly it took me two minutes to convert DAC to AAC. It's the exact same formula with different starting variables.
I got my start using THAC0. Never had a problem with it. The attack roll table in BECMI tho is super simple.
I feel like people (myself included) need to spend a lot longer mentally subtracting numbers than adding them. This might be why descending armor class was such a mental burden and why THAC0 ended up frustrating players.
For me being dyslexic, northing was worse then the dreaded "zero". I always kept skipping 0 as a value and my attacks were off by one. Now that I have my trusty cell phn app. I am much braver to THAC0.
Thank you for this. As a new DM going into BECMI this takes a load off!
THACO is one of the hardest sells for folks I know in re: old editions. I think you’re right in that the simple little table was a better option for a lot of people.
You, or the DM, can just add the target's AC to your d20 attack roll (plus bonuses). If it meets or beats your THAC0 it's a hit. No need to subtract the AC from the THAC0 at all. The 1e way of having 5x 20s in a row confused things a bit, but 2e sorted that out. That's how we played it for 15 years anyway!!
Excellent. I remember doing the double chart method back in college.
I prefer ascending AC but never found THACO to be hard.
We used to use THAC0 the other way around. Deduct the 1D20 roll from your THAC0 and that's the AC you hit.
Precisely! Though remember to add the relevant modifiers to your roll roll first! Then say "I hit AC x" and get told. what happens.
I never thought much about THAC0. It is convenient for some, but definitely not a requirement to play using descending AC.
In my day, we used to subtract the result of the d20 from our Thac0. The difference gave us the armor class that our characters would hit. For example, if I have a Thac0 of 18 and I roll a 15 on my d20, I know I have hit an armor class of 3.
That's how we did it, too. TBH, that's how the rules seemed to say it should be done, IIRC.
Yep same here. Always confused us why no one else understood that haha.
Agreed! I never understood why this was complicated.
Precisely!
The shadow of THAC0 is still buried deep within the 5e DMG under handling Mobs in combat.
I think descending AC is the weirdest hill to die on. If I'd play D&D I would take the book and cross out the descending armor classes and write in the ascending ones.
Make the game more playable. Keep the fire not the ashes.
I adopted THAC0 early, since it was way easier for me as the GM rather than bother with to hit tables for the monsters. I could just quickly figure out what numbers I needed to roll to hit each PC from one number and their ACs. Also, it was easy enough to add the bonuses to the dice roll: if your THAC0 was say 15, and you had STR bonus +2, and you rolled a 14... 14+2 = 16, I hit AC -1, GM, is it enough?
I am glad to have scrolled the comments and see others who finally get it. It warms my grognard heart to see. Maybe there is hope for the younger generations.
But why would players need to figure out how THACO works? Why use tables for this? I prefer the method of "just roll the dice and dm tells you if you hit".
Thank you for your work.
Personally, I only play with THACO, I feel more comfortable with it.
And I know your channel is focused on BECMI.
But for Halloween, a video on the Psi-Blast of Advanced Dungeons and Dragons 1st edition. It'll be fun. And especially on the possibilities of using these rules in BECMI. 🐙🧠🙂
THAC0 was just part of the game when I played it in the 90's. But it was always one of the more fiddly bits and you had to pay closer attention to it than was really warranted for a base mechanic that told you whether you could hit something or not.
When I ran AD&D 2e for a few players who started with 3.x or 5e a few years ago I told them THAC0 was optional. I explained the concept then gave them each a printed chart mapping THAC0 to Base Attack and = 3e armor. It only takes 21 lines to do this (earlier versions stop at -10/30 AC for PCs and if the game went long enough for them to encounter something with armor beyond this I was confident they would be able to adjust by then). The OSR games i've seen seem to go the same route or just adopt Base Attack and ascending AC from 3e+ outright.
Dude, if the slow kid in remedial math in my 7th grade game could figure out THAC0, anyone can figure out THAC0. People just want something to complain about.
As a Moldvay Basic and then 1st Ed AD&D DM, I happily used THACO for my monsters' attacks, but since I never told my players the AC or HP of monsters, just whether they hit (per the table taped to my screen, and my notes of their stats etc) and the visible effects of damage they rolled, it never came up for us.
Coming back to GMing D&D with 5th Ed, and with far less time and mental agility at my disposal, I can't say I missed To-Hit tables or descending AC one tiny bit.
However, having recently played in an excellent BECMI game, I noticed that our DM took the exact same approach to the whole matter as I had in the '80s, aside from the occasional discouraging "you need a 16", which upped the tension.
I started with 1E. When 2E came out I got THAC0 and thought it was better then referring to the Attack Roll Table all the time. What I didn't know about at the time was the AC To Hit chart on Basic D&D character sheets. Never could understand why it wasn't carried over to AD&D...
I am dyslexic and hate math (mild discalclia) and used THACO to make my own attack matrix tables. I started with BECMI when I was 9 years old… so when 2nd Edition came out THACO threw me off… but … my best friends explained it to me and showed me how it worked. He is an engineer now, I am an artist. Eventually this was the only reason why I grasped algebra in 7th grade. Lol😅. If I could do it, clearly anyone can… what is required is a good explanation. Thank you for helping.
Loved hearing about this. Stuff like this can be taken for granted in the wider design. Thanks for being candid in your comment and being open about your experience. It’s appreciated.
This was not my experience wrangling THAC0 with dyscalculia. It was a nightmare.
Such a shame that THAC0 is seen as needing eradication, the big red cross out symbol makes things pretty clear from you. If it's of help to DM's - even as just a short-hand aide like Gary intended, then it has utility. But such is the way with rules development and player accessibility needing to be worked with. I like BOTH descending and ascending AC and am conversant enough to use THAC0 - to me this type of content can be mis-used to be deliberately divisive and exclusionary. (EDIT: As already proved by this very comment section :( ) Having said this, I would never impose a mechanic on players uncomfortable with it. I like OSE's approach to AC - making both of them an option to choose.
But I will still love my BECMI rules. Even published content that embraces THACO in stat blocks. Page 108 in the Rules Cyclopedia talks about this and has a reasonably good explanation of it. I also have a soft spot for 1e and even 2e AD&D :)
Cool video as always though.
Admittedly, the No THAC0 symbol was a bit strong.
@@becmiberserker All good. Love your content. Truly :)
Great video!
Oh also I realise you'll also be at Norwich Games Con! We should defo cross paths if you're game
Always happy to meet people. See you there. 🙂
THAC0 was so nice to use. One of the things I think 2e really got right. Still can’t understand what the problem was for people. We were just kids and that basic math was well within our grasp. If you didn’t want to do the math on the fly, it was a matter of a minute to write a simple one liner on your character sheet with the calculations.
I think the to hit table was from wargames. Especially when only d6 was used, the table allowed more results with attack strength vs defense. A table matrix gives more depth with less complexity.
My thoughts exactly. I'm a miniatures wargamer myself, so I can easily see the to-hit tables as something inherited from wargames rules, particularly considering Gary Gygax's previous career as a wargames rules designer.
Great explainer. It's why my custom sheet over on Pandius has the attack table instead of just a spot for thac0
I’m a huge fan of the thaco system….!!!!
It's not that the maths in hard but that its an acronym and multi step process that you might have to repeat half a dozen times on the fly.
Where as a look up chart is the doing the hard part once at your leisure not mid game and just doing less math every time.
AC = THACO - Adjusted ROLL Dunno if I recall correctly but I think that was how we did it to avoid the tables.
The Best AC you can hit, that is. (Just avoiding confusion :) )
I never had an issue with THAC0, of course I also played 1st ed of Twilight 2000 by GDW, and the character creation system of that game was the very definition of clunky. Cool video :).
Thac0 is great for a DM to avoid large table of small print where you have to scan and your eyes could easy skip up or down a line. I included in all my stat blocks for this convenience, but I never ask players to use it -- just roll and tell me the results and I tell if they hit. It would be nice if they all learned just to better understand the game, but at this point I don't think everyone will.
It was easy and you are the first person aside from my groups I have ever seen get it. d20+mods-ThAC0=AC you hit. The DM will tell you the rest. So bloody simple.
Using thac0 is actually a lot simpler than having to check a table all the time and you do not even need to know the AC you have to hit.
Just roll a d20, add all the pertinent attack roll modifiers, then subtract the result from your thac0. That's the AC you have hit. Announce it and the DM will tell you if you have hit your foe or not.
You only need to write one number and a few specific modifiers on your sheet, not an entire array of tables. And the DM doesn't need to spoiler you your foe's stats. Also, using it this way the descending AC is ininfluent, since it is not involved in calculations.
The DM can do the same for monsters.
Modern games with ascending AC are only slightly simpler, since they do not require you to subtract anything. The result of your roll plus modifiers is already the AC you have hit. AC 0 in modern games is 20.
Great video and I agree on all point and to add video... The last third is the classic TT game issue of "Where to put the crunch" which yes as a player it's easy as you only need to mess with descending armor class once per level up weapon/spell get... But as the DM? Like to me the DM should be the one saying what the players need to hhit inn a system like this... So they have to reference the table at leastt once while adding the monsters and add the AC for all players to that monster stat block... Fortunately you should have their character sheets but still I would never try something onn the fly inn combat or any low prep suff... Which how I do itt in my game system is armor is just another bar of health that normally needs to be depleted sooner and some weapons bypass other do more damage to it... But the to hit in combat unless the GM says other wise is based soly on the weapon and like a wargame you roll each dice a see they hit or not if that do they do damage and you might be able to do more damage if you artubies/ gear/ablities says you can... Yes complex to describe but easy and fast to play. Edit: Which where I want my crunch is on my the developer or on a homebrewer and keep it away from actual play as much as possible.
Great video. I have no dog in the fight, but have never nor will ever use THAC0. I have always disliked descending armor class and tables in combat. All of your points are great, but they are why I use other systems and games. I'll be referencing you and your work in my future videos (should I get around to producing them).
Never played tabletop, but I did play Baldurs Gate on PC when it was released and boy oh boy was this system confusing. Didn't help that I was a kid and English wasn't my native language, but I somehow managed to beat the game. Even seeing the word THAC0 gives me shivers, and not the good kind.
I realized a couple years ago that THAC0 and the old hit tables were really just poorly explained.
They basically translate everything onto an attack roll modifier. Target number of 20, modified by class/level and enemy AC.
Which, was then transformed into the base AC of 10 for an unarmored, average combatant. In both systems, that's true. But now, the AC is no longer a modifier, but a target number of its own.
Ironically, I think the tables, while a handy shortcut, like you said, contributed to this mysticism around THAC0.
The other point was different weapons gave bonuses to different types of AC's. So a fighter could have a reason to switch to war hammer to hit that heavy plate armor. Back when player skill was paramount over class build and features. Not to mention a round was a minute, and weapon speeds were in segments of 6 seconds. That was shocking to me first time playing 5E. When I realized we were running around genetically at 6 second weapon speed segments, and not strategic minutes. It was an abstraction before. Where a war hammer took more segments to generate a hit in the round, but was more effective at hitting and with a much higher damage. Again, not to mention the fighters having better chances to hit than anyone. And different classes advanced at different rates, because experience point requirements were different. The thieves developed quicker, and we're better at what they did. And fighters slower, but still developed quicker at excelling at what they were designed to be good at. And The glass canon magic users slower with some spells taking a number of rounds to cast (making the magic user a target of the enemy and needed group tactics to protect), because -magic missile auto hit, and fireball massive area of effect and damage output...
The thing that I liked about THAC0 was the fact that fighters had a superior chance to hit difficult targets, while other classes had a worse chance. This meant that fighters were vastly superior in their bailiwick, i.e , marshal combat. The standard proficiency bonus of 5th edition levels the playing field to the detriment of the game. If all classes can be good at all things, why even have a class system in the first place?
Back in the day, doing a bit of mental subtraction didn't feel difficult, mainly because our groups DM was a math nerd, and he'd work it out very quickly. I never understood why people found the concept difficult.
Good vid, Berserker 🤘
THAC0 is not complicated, never was, but when charts, etc are introduced, casual players eyes go wide and a lump forms in their throat.
Knowing your THAC0 for your class at your level is enough. Roll a d20, add your modifiers and look at the little THAC0 bar at the bottom of your sheet. Or, roll, add modifiers and tell your DM what you got, and they will tell you if you hit or not (every self respecting DM running a game using THAC0 should have a THAC0 chart within quick reference reach).
Initial fear of THAC0 is quickly overcome, and is easy to pick up, once you have played with it a little.
That being said, I haven't played a D&D game using THACO, since the 90's 😅 Not for lack of want, though.
Keep up the good work, Sir 🤘
All my saving throwing ive been needing to make these days are constitution checks for the lasting effects of sleep spells. THACO reminds me alot of the infamous Warhammer table top games's Weapon Skill Chart and Strenth vs toughness chart they made for their series of games, ive used them for decades and they are quite efficient, epecially once youve memorized them.
I got my start with 3rd edition, so what I've personally never understood about attack matrices or THAC0 is how the player is supposed to declare the result of their attack roll. Presumably an "old school" DM wouldn't divulge the enemy's AC, so does the player just say, for example, "I hit AC 1" and the DM then reveals whether or not it's a hit?
That’s about right. 🙂
When I introduced THAC0 to 5e people, I simply said you don't need to do any maths, not even basic arithmetic. write the table according to the corresponding class you have. if you have bonus, move the result to your right, if it's penalty, move to the left. All you need is to count how many bonus/penalty you have, then look up the AC you hit. When I showed the table, everyone immediately understood.
It would be better to have a similar scale on the AC on character sheet as well, make them circle their current AC, if there's bonus move to right and left for penalty.
That leaves the only mental gymnastic which everyone still need to realize when I report I hit an AC number, is that if it's lower than your armor it means I hit not miss.
THAC0 seems fine to me tbh.
Instead of having proficiency bonuses like in 5e it has a more personalized way to calculate the to-hit modifier that you get from your class.
It reminds me of the to hit bonuses 3.5e characters got from their classes.
An even simpler solution, and the one my own table has used, is to let the DM tell you what your PC needs to hit a particular foe. Give the DM your THAC0 and he/she can work out what you need to hit and tell the player that number. Players don't need to know the AC of their foes (but will work that out in time) and the DM does all the heavy lifting. If the DM can't work out the numbers then they shouldn't be a DM.
I think the main problem is that lots of DMs won't say what the opponent's armor class is.
That's even easier for players, then, since all they need to do is make an attack roll and let the DM interpret it.
Easy: roll d20, subtract from THAC0 & that gives the AC you hit. Say that to the DM & DM tells you whether or not you hit.
I never got that. Ok, I suppose that a few people might game the system by knowing the exact number. On the other hand, you as an actual character would know how hard it would be to hit a person, once you had started a combat. If you started a combat, and knew that the AC was -8, I as a player would try to get away in the same way that the character would realise that all their attacks were being blocked, and combat was hopeless.
@@markbertenshaw3977
It often doesn't matter anyway. If a given character misses with a 13 and then later hits with a 14, the DM has effectively told everyone the target's AC and might as well have just done so from the start.
@@willmistrettaNo. The mystery and discovery is a way to make D&D realistic and more enjoyable for many people, like myself.
It’s like the difference between seeing the entire dungeon map at the start of an exploration, or gradually discovering it (& mapping it) as we explore.
I've never had any sympathy for THAC0, and zero nostalgia for it. For one, my dyscalculia made it a nightmare for everyone. Second, I mean, it's such grognard bs, right? Complicated for the sake of being complicated. It's like that party everyone brags about going to: if you remember it fondly, you weren't there.
While clearly a divisive mechanic which some had difficulty with, personally I found THAC0 vastly quicker and more convenient than attack grids and combat wheels. I don't recall ever issues with players not understanding its use, or having to explain it multiple times. No shade thrown on those who found it troublesome or simply disliked it, but it's as simple as "roll, subtract, go" and frankly, I never understand the reasons it is so reviled.
Another good video.
I guess I'm in the camp of not understanding what is so hard about THACO.
Better than AC 0 you add and if it went the other way you subtract.
I guess if you want to make it easy then just make your self a to hit chart for your PC and then just adjust for ability scores and magic items ( the +1 sword ).
Once again a good video representing OSR gaming and BECM.
AC isn't always known with certainty to the players, or at least for the first few rounds. So our table convention is to subtract the modified die roll from the THAC0. Then they can say "I hit AC (N)." If that bar is too high, then Hero Quest might be a better fit, a game everyone can enjoy, myself included!
I liked Thac0, it made sense to me when I first played. But I had friends who never understood their attacks until 3rd edition came out. As I write my homebrew rules for an old school game now I am using ascending AC and attack bonuses. It is so players can more easily understand the game.
I've never played properly played any edition of D&D, but I understand that the concept of a "lower" AC being better throws players off who have been trained to see higher numbers as better. I've seen alternative ascending AC offered up, but I've never understood why players wouldn't just change the minus in descending AC to a plus, and adding a minus to the "high" ACs. The intention being that the AC is added or subtracted to the attacker's THAC0 to generate the attacker's target number to hit.
So I would change it from;
2 / 1 / 0 / -1 / -2
Into something like;
-2 / -1 / 0 / +1 / +2
I assume that would be an easy fix, unless I'm mistaken.
Good morning, sir. You have commented about retro clones games with ascending armour class system. One of those i recently know is Castles & Crusades. I would really appreciate your opinion about that game. Thanks a lot for your work.
Playing RC now, having come from OSE, so we just convert THAC0/Descending AC to To Hit bonus/Ascending AC. It’s easy. For BX/BECMI/RC:
19 - Descending AC = Ascending AC
For Characters: 19 - THAC0 = To Hit bonus
For Monsters: If HD has a plus, To Hit bonus equals HD; if HD doesn’t have a plus, To Hit bonus equals HD-1.
Players still reference the same THAC0 for their class/level, and still add ability/magic mods as normal. Convert away!
I like THAC0. While I agree it didn't improve much for BECMI I think it was an improvement over the AD&D attack tables. Since those were located in the DMG we used to have the player's announce their adjusted roll, then the DM would have to look up whether the player hit in the DMG and let the player know. THAC0 made 2E combat a bit faster and less onerous for the DM.
I really feel like wotc, and fans of 3e trying to get new players or ad&d players to join up, that REALLY drummed up the thaco=bad narrative. It was a dramatic change and everyone was trying to get those on the fence on board with the new ways. IMO Descending AC was the only problem with the old system, and thac0 took the fall for it.
E.G. For all the 5e players who complain that you shouldnt have to subtract to figure out your hit roll (thac0), I ask them how many times they've done the following: "so the enemy has a 16 AC? Let's see, my total bonuses are +7, so I need to roll a... 9 to hit!" Subtracting to figure out what to hit is apparently fine in d20 systems, but not fine with thac0.
i never got confused with it because i never went to 2e or later. B/X and 1e have the tables. Nice review tho.
Hey BECMI Berserker. I really enjoy your videos but this one still had me scratching my head a bit.
I’ve not played Descending Armour Class before as I started in 3E and later, so I was hoping that this video could clear it up for me. I think part of the problem for me is the with the ‘AC’ in the acronym I keep on thinking of the defence rather than just calling, as you called it briefly, the “Attack Roll”.
So THAc0 is the attack roll & is how hard you hit.
If I’m attacking a Yeti with an AC of 6, and my Attack Roll is 18, then I’ve got to roll an attack of 12 or higher to hit. (That being 18 - 6 = 12)
If I’m rolling against Eclavdra, the Drow High Priestess who has an AC of -6, then I’ve got the impossible task of trying to roll a 24 to hit off a d20. (That being 18 - (-6) = 18 + 6= 24). It is times like that I wished I played DCC so I can use the d24 and d30 dice!
Have I got all this right?
You've got it.
I think so, assuming that what you’re referring to as the Attack Roll value being what you need to hit an AC of 0. Thanks for watching my videos by the way.
oh also, in a competently-run 2e game, players shouldve never had to deal with thac0 anyway - all the players have to do is roll, add their mods, then the DM checks the thac0 and AC to determine whether they hit. Thats how I run my 2e campaign, and thats how I ran my intro adventure the last convention I went to. My players, all coming from 3e and 5e, all had an overall positive "I wonder what all the thac0 fuss was about?" impression from the sessions
THAC0 is an elegant system but Zeb Cook messed up when he explained it with subtraction. Human beings in general find addition easier than subtraction (and more pleasing cause number go up make brain release the happy drugs). The 1991 Black Box edition of the Basic rules explained it completely by using addition and have the THAC0 be the Target Number. If they explained it that way and called it something easier like "Attack Number" or "Hit Number", it would be more well-liked.
If you really don't like THAC0, OSE has a table to convert THAC0 to Attack Bonus/ascending armour class. It's pretty simple and doesn't really impact anything outside of it.
I played 2e for many years with some really smart people with good maths skills. We never got used to thac0.
Yup. One of the weirdest things about it!
D20 + (modifiers including target AC) vs thac0
Or
D20 + (modifiers including ones added in later editions) vs AC
It's no more or less complicated I played the game back in the day and I remember a lot of people explaining it completely incorrectly and trying to reverse engineer it so that AC ended up being the target number.
But it's just a simple as later editions. Fear over thac0 is so weird.
Finally, some that explains THAC0 in a way I can understand! I had already figured out the To Hit Table's about a month ago but was still struggling with THAC0, thank you for showing how to finally solve this puzzle.
Guys, here's how easy THACO is. Ready?
Player: "My THACO is 17"
DM: "Roll to attack"
Player: (rolling d20) "12, I hit AC 5"
DM: (Looking at goblins' AC 6) "That's a hit. Roll damage"
Any questions?
Never had a problem with THACO.
back in 2e days we used to do this: 1. roll dice and add any mods from str/dex and magic weapon mod 2. substract the roll from Thac0 3. declare the AC hit to the DM 4. DM would say you hit or not. This created mystery tension and good anger. Love Thac0. Modern AC is boring
Guys: 20 - thac0 = your bonus. 20 - descending ac = ascending ac. Thats it.
I never really had a problem with THAC0 - it made sense as a quick shorthand for the tables, with AC0 being in the middle of the AC 'continuum' (ok, not a real continuum). I used to calculate my bonuses and then write down that THAC0, so an atatck was a mere 'whats the AC' question (just like 5e, now). That said, my experience is not everyones, and people can now choose which they like - and thats a good thing!
I run a weekly BECMI D&D game that started during the pandemic. The player's ages are 8, 10, and three 12 year olds. They were 3 years younger when it started (except for the 8 year old, who was 6 when he stated. He plays an Ogre so it works with his little kid mentality. But none of them have a problem with subtracting AC from Thac0, not even the Ogre.
What many people miss, is that Thac0 is what makes combat at higher levels work in BECMI, and its absence is what makes high level combat in d20 so meh.
This is all so silly. THACO is so simple and it's so helpful as a DM. Essentially, with the ascending Armor classes the designers simply pulled the bonus PCs get out of the table and made it a plus that they add to their dice roll. Then they roll against the higher number. Descending Armor Class bakes that bonus into the table, so you simply subtract your foe's AC from the THACO number on the table. It's one number with the attack bonus baked into it.
Honestly they are 6 of one or a half-dozen of the other. Either way it's the same!
I personally prefer Descending AC/THACO because it is simpler to me. I have my THACO, all I need is my foe's AC and I know the to hit number.
I run an AD&D Fighter named Cei. He uses a two-handed sword +1, has 17 Strength (+1 to hit), and is a 5th Level Fighter. According to the newer OSRIC book page 14 he has a basic THACO of 16. So I load that number up a bit by subtracting my other bonus' from that: Sword -1, Str -1. That gives me an overall THACO of 14. That's all I need to write on my character sheet- THACO 14. Why a 14? Because that's literally what I need to roll on my D20 to hit AC 0. From there all I do is subtract positive ACs or add negative ACs and I get exactly the # I need. It's isn't tough math. Let's say that I need to hit a well protected Orc lord who has an AC 3. I simply subtract that 3 from my THACO of 14- I need a 11 on my die roll. With THACO I've done all of my math work BEFORE the game and not DURING the game that most people do with ascending AC (which speeds up the GAME!). Now all I need to do is just subtract a foe's AC from my THACO and I'm good to go. If the DM tosses in modifiers then I just account for them when I roll. Let's say he's stunned, so I got a +2 to hit. Easy to do. I just tick off another two from my to hit. My 11 now becomes a 9.
For a lot of people it's confusing as you're reversing everything because the original attack bonus is baked into the to hit chart. For example, a 1st Level Fighter has a THACO of 20. That's a +0 attack bonus while my Cei, 5th Level, has a basic THACO of 16 which is four less than the 20. That means that Cei has an attack bonus of +4 in the modern system (modern fighters get a +3, but they are better off as they get another attack at 5th... AD&D has to wait until 6th level and even them is just 3 attacks every two rounds... :( ). Anyway, modern D&D just strips the attack bonus you get at higher levels out of the attack chart and puts them facing the players rather than bakes them into the attack chart and hides them from players (DM faced).
At the end of the day, it's literally the SAME THING math wise. However I do get why many people prefer ascending ACs. The math appears to be simpler because it's player facing.
Anybody ever subtract their d20 roll from their THAC0 to see what AC they hit? You know, for those DMs that kept AC of monsters a secret. THAC0 18 minus roll of 13 means you hit AC 5 or worse.
This can be so much easier. The players only need to roll a d20 and add the relevant modifier. Give that result to the DM.
The DM adds the enemy's AC to that and compares to the player's THAC0.
Is the total higher than their THAC0? If so, they hit.
A level 4 Fighter rolls a 12 and adds +2 for high STR. 14.
The goblin that they hit has AC 6, so the DM adds that. Total of 20.
20 is equal or higher than THAC0 17, so the fighter hits the goblin. Roll damage.
This makes it virtually the same as adding up bonuses and whatnot in 5e.