Let's Talk About THAC0

Retreater

Adventurer
In the day we called it "THACK - oh" though I've now started pronouncing it "THAY-koh."

And even though I was with AD&D 2nd edition since about the start of that edition, the concept of THAC0 was a major stumbling block and not intuitive. I'm glad it's gone, and if I were to run 2e again, I would convert to modern ascending AC and attack bonuses.
 

Lanefan

Victoria Rules
THAC0 was first introduced to AD&D (1st Edition) as a usable game mechanic in 1983 with the module "UK3: The Sentinel" as an optional rule.

It latter appeared as an "official" part of the 1st edition ruleset in 1986 with the publication of the "Dungeoneer's Survival Guide" hardbound.
I could be wrong, but I'm fairly sure THAC0 was kicking around in Basic before this - which probably explains some of the confusion, as many of us kinda lumped Basic and AD&D together at the time mostly by using Basic modules in AD&D games.

However, that said, neither the Combat Matrices nor THAC0 keep the player from determining the AC of any opponent they face.

The way you do it, the player can easily determine the AC of their opponent by the process of elimination... "Well, a 14 did not hit, but a 15 does, so that orc's AC must be at least 3".
This, however, I don't mind - it reflects the warrior learning more about the foe she's facing as the combat goes on. And there's still some guesswork involved - OK a 14 misses and a 15 hits, but if I don't know my combat-matrix position (a.k.a. BAB) I don't know how much of my success is coming from that vs. how much is related to the foe's AC.
 

Beleriphon

Totally Awesome Pirate Brain
Ha, that was my understanding.

Follow up question: Would ''THACO'' be a feminine or masculine word? Believe it or not, this as been the subject of many friendly debate at my table :p . For those who speak french, would it be ''le THACO'' or ''la THACO''? There's unfortunately no true neutral in french.

Thanks for your time, this thread will help me assert my DM domination over my table :p

As for the mechanic itself, once it is explained like this its indeed quite easy, I dont know why I thought it was way more obscure than that.

On French, THAC0 is an acryonym of To-Hit Armour Class 0; so I'd go with whatever gendered pronoun you'd use for Armour Class in French.

As for the math, its very clearly: (Die roll + Modifiers) - THAC0 score = AC Hit

Thus, a roll of (13 + 2 for a magic weapon) - THAC0 18 = 3, so we hit AC of 3.

The issue is that in the AD&D rules at any point actually explain the process of attacking in that way. So the process isn't hard at all, its not really that much harder than d20 roll + BAB + Mods = AC. The difference is that the rules in 3E explain this all very clearly in the rules dealing with attacks.

The other big difference is that AD&D had a bunch of disparate subsystems that didn't really add up the same since some were roll under with modifiers to die rolls, others were roll over with modifiers to die rolls, some were roll under with modifiers to target numbers.

On the last one look at saving throws. A bonus from some kind of item was say +2 to Save vs Wands. That's actually a bonus to the score, so if your character had a score of 16in that save category, while wearing the magic item it became 18, which only fails on a 19 or 20, rather than a 17 through 20.

The biggest change 3E did was consolidate the way rolls were made to begin with. THAC0 is easy enough, but there is no reason it should be a completely different set of math for task resolution from every other task resolution in the game. So it should either all work like THAC0, or should all work like something else, but having a dozen different methods to calculate success from rolling a d20 is why THAC0 has a bad reputation, its the poster child for mismatched task resolutions.
 
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Oofta

Title? I don't need no stinkin' title.
So ... you don't accept that some people found THAC0 painful? You keep asking people to explain it to you. It's simple. Some people find it more difficult. Period. End of story.

You ask "why" ... well the answer is that apparently not everyone thinks like you do. My wife started playing D&D with 2E and she hates THAC0 because it makes her subtract and she finds the numbers (especially negatives) confusing. She's a lot smarter than me (and most people for that matter) in a lot of ways, but she would never go back to 2E because of the "backwards math".

I can't give you a better explanation, nobody can. Some people find it more difficult and greatly prefer the way the rules changed for 3. That's either something you can accept or not.
 

Morrus

Well, that was fun
Staff member
So ... you don't accept that some people found THAC0 painful? You keep asking people to explain it to you. It's simple. Some people find it more difficult. Period. End of story.
Woosh. :)

It’s a joke.
 

Staffan

Adventurer
The same goes for saving throws vs attack spells. There's no mathematical difference between a caster rolling an attack and his target rolling a save - the distinction is just needless complexity.
Except that the difference creates real differences in who's "responsible" for the event and who has the power to affect it. For example, if a character has Inspiration in 5e they can use it to get advantage on an attack roll, but they can't use it to give their opponent disadvantage on their save.
 
Except that the difference creates real differences in who's "responsible" for the event and who has the power to affect it. For example, if a character has Inspiration in 5e they can use it to get advantage on an attack roll, but they can't use it to give their opponent disadvantage on their save.
Sure, that difference is a system artifact.
Conceptually, the attacker is always responsible for the event. He attacked, whether with weapon, cantrip, spell, or quip.

And, both attacker and defender (If not helpless) should, conceptually, be able to affect the outcome.
 

Beleriphon

Totally Awesome Pirate Brain
Sure, that difference is a system artifact.
Conceptually, the attacker is always responsible for the event. He attacked, whether with weapon, cantrip, spell, or quip.

And, both attacker and defender (If not helpless) should, conceptually, be able to affect the outcome.
Star Wars SAGA Edition did this. Everything is an attack, it just depends on what number as the attacker you need to use to be successful. So a grenade is an area attack against the defenders relevant defense scores.
 

billd91

Hobbit on Quest
Star Wars SAGA Edition did this. Everything is an attack, it just depends on what number as the attacker you need to use to be successful. So a grenade is an area attack against the defenders relevant defense scores.
Yeah, but it kept the PCs from using their Force points to defend themselves because they could no longer use one to gain a bonus on their saves. In the end, it felt like a net loss for the system, particularly with respect to the setting and the heroic/Jedi ethos of using the Force for defense in preference to attack.
 

Lanefan

Victoria Rules
As for the math, its very clearly: (Die roll + Modifiers) - THAC0 score = AC Hit

Thus, a roll of (13 + 2 for a magic weapon) - THAC0 18 = 3, so we hit AC of 3.
Even that's counterintuitive, as 15 - 18 = -3, not +3. You skipped mentioning the step that says 'reverse the +/- on the answer given by the formula to get the AC you'll hit'.

Either that, or you got it backwards and it should be [THAC0 - net roll result = AC hit].
 

Staffan

Adventurer
Back in the day, my players didn't have much problem with THAC0, but that was to a large degree because I had made a character sheet that had accommodations for it. I had one row for THAC0 that went something like this:

Base THAC0:____ Melee mod: _____ Melee THAC0: _____ Missile mod: _____ Missile THAC0: _____ Thrown THAC0: _____

Then I had a weapons table which had a column for Attack modifier (which would mainly be specialization and/or magic), and next to that a column for adjusted THAC0. When rolling, the player would calculate THAC0-(d20 + situational modifiers) and tell me the lowest AC they'd hit. At the time this seemed simple, but in retrospect that was just because of a lot of pre-calculations.
 

lowkey13

I'm sorry, Dave. I'm afraid I can't do that.
THAC0 is clearly preferable to BAB, for two reasons.

One, it sounds cooler, and closer to the action of hitting. THAC0. It's an aptonym.

Second, it is easier. As [MENTION=1]Morrus[/MENTION] has repeatedly explained to the rest of you, addition is easier.

With THACO, you are always adding.

With BAB, you have to constantly subtract negative numbers.

So NOT ONLY do you have to use subtraction (OH NOES!), you ALSO have to subtract negative numbers. I swear, if I ever have to subtract the negative of the proficiency again ....

Stop bowing to the tyranny of math.
 

Sacrosanct

Legend
There are two observations whenever we have discussions like that that always make me raise my eyebrows a bit.

1. The claim that THAC0 is too difficult, or that people have a difficult time figuring it out. Why? Because you're doing tougher math every time you take damage, or gain or spend your coinage treasure. If someone is having a tough time trying to figure out: THAC0-modified die roll, then certainly they have a hard time figuring out: current HP-modified damage taken or current gp - how much you spend. After all, with HP and gold, the numbers are often greater than less than 20 (which is the highest variance you'd typically find in THAC0, often much less).

2. The claim that when 3e came out, ascending was much easier. I mean, sure, on the surface ascending is more intuitive than descending, but 3e also brought with it a ton of extra modifiers, and huge numbers bloat, along with it. So in actual play, you did a lot more steps in 3e than in 2e. 3e not only had many more things that modified your rolls over 2e, but it also brought more complexity with things like 3 different ACs, and different attack bonuses depending on which attack you were making (2nd and subsequent attacks). So while ascending is more intuitive than descending, 3e compared to 2e was more complex.
 

billd91

Hobbit on Quest
2. The claim that when 3e came out, ascending was much easier. I mean, sure, on the surface ascending is more intuitive than descending, but 3e also brought with it a ton of extra modifiers, and huge numbers bloat, along with it. So in actual play, you did a lot more steps in 3e than in 2e. 3e not only had many more things that modified your rolls over 2e, but it also brought more complexity with things like 3 different ACs, and different attack bonuses depending on which attack you were making (2nd and subsequent attacks). So while ascending is more intuitive than descending, 3e compared to 2e was more complex.
Whenever I read people comparing the complexity of the two editions (2nd and 3rd), I usually find how many people forget the complexity 2e had to offer. For example, there may have been multiple ACs in 3e, but there were caveats with AC in 2e as well. Did you use a shield? If so, your AC depended on facing and position as well as how many attacks were directed at you from the directions covered by the shield - so that's at least 3 ACs right there. Plus, there are times (and positions) where Dexterity adjustments do not apply. Ultimately, 3e isn't really more complex so much as it formalizes a few of the ACs so they're more obvious to the end users - the players. The lack of obviousness of the other ACs may have allowed individual tables to simply ignore them, but doing so didn't make the game as written less complex.

3e's iterative attack bonus may have been a little more complex, but it served as an alternative way to operationalize AD&D's half-step attack rates so players no longer needed to worry about whether not it was a round in which they got 2 attacks or just 1 with their 3/2 attack rate. It traded one complexity for another.

The one place 3e really is more complex is in the number of buffs that could apply. But with those, players could self-regulate. If they found tracking too many modifiers a drag, they were fully in control of how many they used.

And as far as tracking hit points complexity - there's a reason some players add up damage to compare with their max hit points rather than subtract damage from their current hit points. They get to trade the subtraction they find more difficult with the addition they find easier. And with the spending of gold? That's usually not in combat round time, so calculating that doesn't really hold up play time very much.
 

Gradine

Archivist
To be brutally honest, the whole way BAB worked with multiple attacks/full attack action was probably one of the worst 3.X-isms.

Though still better than 3/2 attacks per round nonsense.
 

lowkey13

I'm sorry, Dave. I'm afraid I can't do that.
Though still better than 3/2 attacks per round nonsense.
My fourth level monk, with 5 attacks per 4 rounds, LAUGHS at your concepts of nonsense.

Combats with a fourth level monk in AD&D are similar to long road trips with small kids ...

"Is it the fourth round yet?"
No.

"Is it the fourth round yet?"
No.

"Is it the fourth round yet?"
No.

"Is it the fourth round yet?"
No.

"Is it the fourth round yet?"
No.

"Is it the fourth round yet?"
No.

"Is it the fourth round yet?"
No.

"Is it the fourth round yet?"
No.


"Is it the fourth round yet?"
.....
SHUT UP!
 

Beleriphon

Totally Awesome Pirate Brain
Could they use it for a bonus to AC, before, too? Seems like Jedi do a lot of dodging and blocking.
A Jedi character could use abilities to boost rolls affecting their ability to block attacks with a lightsaber, or outright rebound blaster fire.
 

Beleriphon

Totally Awesome Pirate Brain
Even that's counterintuitive, as 15 - 18 = -3, not +3. You skipped mentioning the step that says 'reverse the +/- on the answer given by the formula to get the AC you'll hit'.

Either that, or you got it backwards and it should be [THAC0 - net roll result = AC hit].
I totally did, which just goes to show that subtraction is not the way to go.
 
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