One flips through gaming books and sees all of these numbers
and hears complex terms like COMBAT MATRIX, descending armor class, combat
modifiers. The deal is that it is harder to talk about math than it is to just
solve the problem. None of the math problems that we’ll have to solve during
play will involve any tool more advanced than a basic calculator, and everybody
can use a calculator! Once you get going with the system it forms an algorithm
and players can quickly do the math in their head, as it isn’t anything that
you don’t do every day anyway.
THAC0 simple means, “To Hit Armor Class 0” When the second edition
included this as core, it revolutionized the game, sort of. It was always kind
of there, but what it allowed was for us to write down just one number on our
character sheets and this would help us figure out what we needed to roll to
hit a target regardless of how challenging the target was to hit.
Inventing a system this easy to use took a lot of testing
and tinkering, prior to Dungeons and Dragons, the game’s inventers played
wargames, and one always had to come up with a system which randomized if a hit
was successful or not in a fast and concise manner. Dice proved a great
universal method. Once we figure out a system, then we have to figure out how
to describe the system so that others can use it as well, which since math is
never changing, math is the best way to figure all of this stuff out.
Prior to the THAC0 system, the game designers created Combat
Matrixes, tables that when rolled against, told you if you hit or not, some of
these were more complex than others, but they all strove to achieve the same
goal, the more universal the better.
We get the term Armor Class from Wargames as well,
specifically Naval Combat where different ships had different amounts of armor
to protect them, players found that a descending armor class was more
functional in the game than ascending Armor Class systems, but in Naval Combat,
the ships AC never changed, the same goes for all mass combat systems, so when
Gygax wrote the Chainmail Rules, he used a universal Armor Class system shared
by all of the troops in a battalion.
When it came to D&D, the terminology was kept, and we
have the AC system, but instead of a fixed number, the number for an individual
target isn’t constant. A ships ability to hit another ship always stayed the
same, but with individuals we wanted to simulate improvement, this required
some additional thinking, and more complex combat matrixes.
In the first edition of AD&D, players wanted lots of
ways to fight and modify things to make an opponent either easier or harder to
hit depending upon choices that each player made. The AD&D system kept this
matrix hidden from player view by putting it in the DMG, you rolled the dice
and the DM told you if you hit or not. This provided a mystery because you didn’t
know how the DM achieved this target number, as the DM wanted to keep all of
the stats secret. It didn’t work, players caught on to the formula, either from
sneaking a peek at the DMG or just playing enough to realize the DM’s system.
This also required even more work on the DMs part, and users were coming up
with their own methods of changing it up to make it easier for them to come up
with a universal system that could still be modified quickly.
It was a bunch of computer scientists at UCLA who were playing the game
regularly that figured out that you didn’t need the entire combat matrix for
the game to function, that if you just told them how to hit AC 0, and add all
of the modifiers separately, you just needed to know one single number. Gone
were the pages and pages of overly complex combat matrixes. For whatever
reason, Gygax didn’t like it, it is briefly mentioned in the DMG, but dismissed as too simple. Dave Cook however
saw it as the ever elusive universal system so it was officially added to the
2e mechanics, and it made play a lot faster.
Detractors instantly rejected this method, saying that it
dumbed down the game, and others claiming that it made combat too difficult to
figure out. 2e was still learned, not by yourself and on your own, but by
playing the game with others who had been taught by somebody else who already
knew how to play the game. If one looks at the THAC0 system by itself, it can
be confusing, but all it takes is the player sitting next to you to help you
figure out if you hit or not for a couple of sessions before it is permanently
implanted in your brain in a way that will never go away . . . ever.
In third edition, they changed descending AC to ascending AC
which really threw 2ers for a loop. You play with this system enough it becomes
ingrained in you and even something as simple as making AC 1 as bad is enough
to throw you off, so I know that going back to a descending AC is the same way
for others, just know that us holdouts didn’t refuse to move on to 3e because
of ascending AC, when it comes down to it, 3e is too ridged of a system when
you get used to the freedom that earlier editions allow.
So what is the formula? Well, it is easy. Look at the THAC0
grid, and find the number you need for your level. This number never changes,
it doesn’t float around, and it is always the same. When you have a modifier
you don’t apply it to your THAC0, you apply it to your opponents Armor Class.
Thus, a sword+3 doesn’t change your THAC0, it changes your opponent’s AC from 4
to 7. Penalties also change your opponents AC, if you have a -2 to your roll,
you take it from his AC, which turns an AC of 4 to an AC of 2.
Simple yet elegant, isn’t it! Suddenly all of the complaints
that it requires to much math are dismissed. The problem wasn’t the system; the
problem was that people kept trying to modify their THAC0 numbers.
Once you get it figured out, and can start playing with more
advanced rules, the THAC0 system still functions. Now you can have missile
combat and melee combat taking place in a forest at the same time using the
same ruleset without having to change anything. The floating AC rule allows
combat to flow smoothly and naturally so that both sides can focus on play
without having to get all technical.
IS THE THAC0 SYSTEM BROKEN?
Broken, no; subjective, very. If you up and decide to use a
different method of deciding how combat is resolved, then you aren’t playing
AD&D. Taking it out makes all of the other rules in the AD&D system not
work anymore, period. The game encourages you to tinker with the AC system,
applying modifiers as you see fit to factor in advantages and disadvantages
depending on where exactly each battle is taking place. Can you get carried
away with modifiers? You bet! And the AD&D system will let you do this, but
the DM can always decide exactly how many or how few of the optional rules and
modifiers work best for their particular game.
We had to go here, I hope that I was able to clear up some
confusion about how the THAC0 system is supposed to work, because it isn’t this
mechanic that weakens the game, but what LOTS of people do with it that does,
which we can now explore.