This Is Chainmail. This is D&D.

[WARNING: This post contains nerdery and numbers. Proceed at your own risk.]

About a year ago I wrote this analysis of the Chainmail mass combat rules. I have this on-again off-again project I’m working on, which basically amounts to a retroclone. Basically I’m looking to write a system that stays very true to the original rules as written, with cool things added on from later iterations of the game in a way that they don’t upset the original spirit. Yes, this is more or less a set of house rules, that I at one point tend to write up in some sort of organized book-like file, more for my own gratification and the people I game with than for public consumption.

This is pretty long and rambly, so here's a picture of what Google assures me is Harold's death as presented in the Bayeux Tapestry.

One of my primary concerns in the crafting of this system is adhering to the rules as presented in Chainmail since the original rules for Dungeons & Dragons mentioned explicitly many times that the rules were to be used in conjunction with Chainmail. For those unfamiliar with that game, there are basically three different levels of combat detailed in Chainmail. The “standard” game is played between armies with figures representing twenty men apiece. The “Man-to-Man” rules deal with skirmish-level combat, where each model is an individual combatant. Fantasy combat deals with contests between fantastic creatures, such as dragons and trolls and the like.

In the post I referenced a year ago, I dealt with the standard 20:1 rules. That post was more-or-less a distillation of the base system, but my thinking at the time was to use that, along with the “Fighting Capacity” designations for each class as detailed in the LBBs, to fight smaller-scale conflicts. I dedicated a great deal of time and effort into making a combat system that would closely follow the guidelines laid down in that post. However, in so doing, I gradually came to the realization that, for the typical combats that my players tend to get into, those rules are just not fun, and any alteration I made to them took them farther from the spirit of the original. I often found myself stuck between that which is true to Chainmail and that which is fun.

So I’m abandoning that train of thought for the time being to focus more on the Man-to-Man rules. Looking at these, it’s much closer to the standard D&D combat with which we’re all familiar. In fact, one could easily just pick up the rules wholesale and drop them into D&D and have a perfectly workable system. So why not just do that? There are two problems.

  • The rules assume all combatants are of equal skill, with the only difference being equipment. Keeping this standard would basically make leveling up a simple matter of better saves and better hit points for the fighter, with no improvement in fighting capability whatsoever.
  • All attacks are rolled on a table, where the attacker’s weapon is cross-referenced with the armor of the defender. This is wonderful for two humanoids in battle, but it is completely unworkable for creatures like dragons, or creatures wielding exotic gear, or bears.

OK, so that first problem can probably just be fixed by giving higher-level fighters some sort of bonus to their die rolls or whatever. I’m not dealing with it at the moment.

The second is more problematic, seeing as how the game is Dungeons & Dragons, and a combat system that doesn’t let you fight dragons doesn’t really gel. So how do we deal with it? One option is simply to assign those monsters the armor that most closely approximates their natural defenses. A troll, with its thick, rubbery hide, might be given a leather armor class, whereas a scaly dragon would get plate. I imagine most animals would be assigned leather or no armor under this system, and we can tack on additional rules, such as small creatures forcing the attacker to subtract 1 from his to-hit roll.

That might be one way to go, but then what happens when those creatures attack? Do we likewise assign them a weapon? What would a dragon’s bite be? The system as written has the effectiveness of certain weapons versus certain armor deeply entrenched, and it seems like trying to shoehorn a bunch of non-humanoids into the mix takes away from the original intent.

The alternative that I propose is to assume that the system as it stands represents not only a weapon’s inherent usefulness against a certain armor type, but a combatant’s knowledge of how exactly to use such weapon to its greatest advantage (and perhaps the defender’s ability to counter those weapons which are easily countered). If we give each armor type an armor class (say, between 9 and 2), we can give each armor class a certain percentage chance to hit, which is used universally. If the combat is between two humanoids, we then have a separate set of modifiers for each weapon against different types of armor. When humanoids fight fantastic creatures, there are no modifiers, representative of the fact that the combat tactics to fight, say, a dragon, are quite exotic to the warrior, so he can’t make use of any inherent advantages his weapon may have over the opponent. If this seems familiar, it’s because it is basically the system used in 1st edition AD&D.

To find the baseline probability to-hit for each armor class, I took the average of every weapon’s ability to hit every armor class, percentage-wise. The results are as follows:

Unarmored (AC 9): 57%
Leather (AC 8): 50%
Shield (AC 7): 42%
Leather & Shield (AC 6): 42%
Chainmail (AC 5): 35%
Chain & Shield (AC 4): 30%
Platemail (AC 3): 15%
Plate & Shield (AC 2): 10%

You’ll note that in the original rules wielding a shield alone is on average better than wearing leather armor with not shield. These percentages can be converted into target numbers. Here I converted these into the number one would need to roll on 2d6, since this is the type of roll used in Chainmail.

AC 9 and AC 8: 7
AC 7 and AC 6: 8
AC 5 and AC 4: 9
AC 3: 10
AC 2: 11

Since the range of results is fairly limited using only 2d6, there is not much variation in targets. These are really approximations of the true average odds, but I think they are the best approximations we can have. Here’s the same table with target numbers using the more familiar (and more granular) d20.

AC 9: 10
AC 8: 11
AC 7: 13
AC 6: 13
AC 5: 14
AC 4: 15
AC 3: 18
AC 2: 19

Basically, we have the standard combat table for 1st level characters, with the exception of AC 7 and the jump to plate mail.  I think this goes to show that Gygax and co. were either very careful to map out the combat table so that it fit with Chainmail, or very careful when writing Chainmail in the first place to have a steady progression. I believe the jump between chain & shield and plate mail is a product of the bell curve distribution of 2d6 versus the linear distribution of the d20, and likewise with the blip at AC 7.

So that’s everything you need to fight those fantastic creatures and bears and whatnot. Roll a die, find their AC, and see if you score a hit! Then, of course, roll 1d6 damage and deduct it from the opponent’s hit points. Rinse and repeat. Soon I’m going to write a post looking at the weapon modifiers, once I figure out how to make nice-looking tables. That’s where things get interesting.


1 Comment

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One response to “This Is Chainmail. This is D&D.

  1. Pingback: Chainmail And Weapon Modifiers | …duck, duck, DIE!!!

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