Monday, November 17, 2008

Weapon vs AC

Particularly in the wake of Third Edition's conflation of the concept of Armor Class with a target number (or Difficulty Class, to use 3e terminology) needed "to hit" an opponent in combat, it's fashionable in many quarters to claim that the OD&D/AD&D approach is somehow inexplicable, or at least anti-intuitive. While I'll grant that the 3e approach is simple -- no charts are necessary to derive the "to hit" number -- I think its simplicity comes at the expense of coherence. What many people forget is that, prior to 3e, Armor Class really was (at least in intention) a class. That is, the AC numbers were designators for different types of armor, each of which had different strengths and weaknesses against different types of weapons. The infamous "weapon vs. AC" tables of Greyhawk and AD&D were intended to make this more plain for the "alternative combat system" of the three little brown books. In Chainmail, whose man-to-man combat system OD&D uses, the connection is quite explicit, with a character's chance "to hit" dependent on the type of weapon he is wielding and the type of armor his opponent is wearing.

You'll note that, in the preceding paragraph, I put "to hit" in quotation marks throughout. There's a reason for that. Remember that, in both OD&D and AD&D, a combat round lasts 1 minute. Even in the case of combatants with multiple attacks per round (like monsters or high-level fighters), it strains credibility to imagine that each attack roll represents a melee action taking up to 60 seconds to execute. In the real world, that's ridiculously slow, even in the case of men encased in plate armor and wielding "slow" weapons. But both games use a very abstract combat system and each attack roll doesn't represent a single attack at all, but a series of attacks over the course of up to 60 seconds, including parries, feints, and other defensive actions intended to make it harder for one's opponent to score a hit.

But what is a "hit?" It has long seemed to me, given the abstract nature of combat, that a "hit" can only be a blow that lands either hard enough or in a vulnerable enough spot that it deals damage to one's opponent. In the course of a melee round, an attacker undoubtedly lands many blows against his opponent, but only those represented by a high enough "to hit" roll deal damage sufficient to subtract hit points from his total.

For this to be workable, even given the abstraction inherent in the system, you need to take into account the peculiarities of weapons against certain types of armor. If you don't, then it becomes harder (to my mind anyway) to figure out just what is happening and what Armor Class is supposed to mean. The Dexterity bonus to AC throws a wrench in the works. I can accept the idea of someone who is nimble being harder "to hit" in combat; that makes sense. However, his nimbleness does not affect his Armor Class, which is a constant. Instead, his Dexterity bonus should serve as a negative modifier on his opponent's chance "to hit." This may seem a small thing, but I think it's important, because otherwise Armor Class acquires some incoherence, particularly if continue to use the weapons vs AC table.

Of course, many people don't -- and never did -- use the weapons vs AC table, seeing it as an unnecessary complication. On some levels, I agree; I often ignored it for large combats back in the day. At the same time, I very much like the feel of fighters choosing their weapons based on the type of defense their opponents possessed. This gives a fighter a reason to carry multiple weapons and it rewards players who consider the benefits of doing so. I approve of that and think the game should encourage it. The only trick, I suspect, is finding a simple way to present the "to hit" numbers based on AC that can then be used in conjunction with the class-based attack matrices. Conquer that "pedagogical" issue and I think most people wouldn't find the weapon vs AC concept quite so off-putting.

But don't get me started on negative AC ...


  1. I always liked the charts, but they are a tad cumbersome. A somewhat workable fix would be to print off "to hit" charts for particular levels of classes (or hit dice of monsters) rather than just particular classes, and instead of mapping level and AC to target numbers, map weapon and AC to target numbers.


  2. I have been using an alternate combat matrix in my games at very little cost in speed. It's very loosely based on the Greyhawk chart, and I've been thinking about tweaking it a bit, but I'm happy with how it has gone thus far. I'd appreciate thoughts on similar attempts at a simplified weapon vs armor matrix.

  3. @Wayne Rossi: That's a handy chart there. Even a simple-minded 3tard like me can make sense of it. ;-)

  4. I used a modified version of AD&D2e's armor vs weapon types in my game. Had each set of armor have a bonus and a penalty to either piercing, slashing or bludgeoning weapons. I would imagine that the attack modifiers based on weapon and armor that I've seen in AD&D1e would just be too slow.

  5. I've tried to incorporate those modifiers, which are essentially from Chainmail, in the past. We ignored them in AD&D, and I still ignore them to this day in OD&D. In my opinion, the whole AC equals the actual armor worn, and the weapon vs. AC tables fall down flat and make no sense in about 95% (in my campaign, anyway) of all encounters. Once one realizes that the PC's are normally fighting monsters with natural/evasive ACs, one realizes that the weapon vs. AC idea is great in a game like Chainmail, but doesn't work as well in D&D.

    That said, I have allowed it's use in the past when something like a one on one duel is in order, whether it be two PC's settling a dispute, or a PC facing a bad-ass NPC. When it is indeed man vs. man, I think it stands up well (but, as you noted, only when you are using the definitive AC, not some adjusted value).

  6. I definitely use that most infamous table regularly. Bear in mind that the "weapon vs. armor class" table in the PBH is intended to be used against the base armor class of the target.

    That is, the modifier is obtained against the actual type of armor; that footman's flail gives you a +2 against someone wearing chain mail even if his dex and magical adjustments eventually bring his AC down to 0.

    That, if I'm reading you right, puts away the issue of the DEX modifier.

  7. I think the OD&D interpretation is really best: armor class describes your armor, not modifiers. When magic armor comes into play, it will be a subtraction from the attacker's to-hit roll rather than from the defender's armor class. This is especially important for my alternate combat matrix.

  8. 1st edition Gamma World uses a pretty strict Weapon Class vs. Armor Class which works pretty well. I'm guessing that with D&D that system "appeared" to be too crude to account for all the new magic weapons and armor and gradually the game lost the original OD&D interpretation in favor of Weapon Speed Factors (themselves, not very popular with gamers). Apparently, the original intent was lost and misinterpreted over the years, and the 3+4e designers, much like Gamma World humans, are still not quite sure what it's really means.

  9. I like the idea of weapon types performing better or worse depending on the armour of the opponent but have never used it in my campaigns, either recently or back when I used to play AD&D 2e. They just slow down play too much, its another modifier you just don't, in the thick of combat.

    But, giving it some thought, an idea occurs to me. Why aren't these just incorporated as part of the armour itself?


    Chainmail, AC 5 vs piercing weapons, AC 7 vs bludgeoning, AC 3 vs slashing

    (just an example, not suggested AC values). Thats pretty easy for everyone to work out; just have three armour class values on your character sheet.

  10. The "Combat Computer" wheel published in Dragon #74 made using the W vs. AC tables much more simple, and manageable.

    Also worth noting is that using the W vs. AC charts---which do encourage fighters to leverage different weapons vs. different foes, as James notes---further reinforce the value and game balance of using weapon proficiencies in your games. If any PC can carry and use any weapon without penalty for non-proficiency, then W vs. AC does become the dinosaur that many folks regard it as.


  11. I think armor class was an unfortunate inheritance from strategic war games. It works well enough, but it's not a selling-point.

  12. Joseph is correct, it is the "base armour class". Dexterity and magical modifiers don't affect armour class for the purpose of the "weapon versus armour". This may not have been clear in OD&D, but it is explicitly mentioned in AD&D.

    It does however, also include the shield, as far as can be determined from the text and table. That is problematic, in my opinion, but it also creates additional diversity.

  13. Thanks to everyone who helped clarify my misapprehensions. This is a case where I was simply mistaken on an important point, namely that the table is intended to be used in conjunction with base AC, not modified. That makes the table work properly and achieve its purpose, one I approve of for many reasons.

    Once again, thanks for showing a grognard some new tricks. Who'd have thought it possible after all these years? :)

  14. I guess I understand the logic at work, but I do think that magical enhancement should affect the AC, not the to-hit chance. Partly, I imagine, because having come into the hobby through Lord of the Rings, I think of magic items as not necessarily being enchanted, but rather made to a standard of quality not truly attainable without bending or outright breaking the mundane laws of physics.

  15. The AC and the to hit chance equate to the same thing - how easy is it to cause damage; however they have been split apart here to simplify the syste - one is applied to the die roll and one is a lookup on the chart

  16. Ive always considered weapon type vs AC to be the "ASLing" of the D&D family. While it is more realistic and detailed, does it really provide that much all things considered?

    I personally have never seen it. I am even dubious on weapon type vs size damage, and that's an easy one to keep track of!

    Its sort of like Verbal/Somatic/Material for spells. It does increase detail and give a more flavorful and realistic feel, but at the end of the day, its better off ignored in the desire for speed, ease of memorization, and excitement factor.

    My problems with D20 can be traced to such things. Its foundation is rock solid and ideal. Then they started throwing all this needless malarkey on top of it and making it as integrated as possible into the game as to make removing it a nightmare scenario.

    (If ASLing doesn't work as a term for what I am saying, howabout the GURPSification of an RPG?)

  17. Has anyone ever worked out an alternate system where certain weapons give damage bonuses vs. certain armor types? That might be a more workable solution than making it easier "to hit".

  18. I want there to be advantages(can use any weapon) and tactical options for fighters like there are for spellcasters.

    My current thinking (influenced by RoleMaster/HARP) is to make a 3x5 card for each weapon a character has.

    This card would include a vs AC chart, damage, weight, any other relevant information.

    I also am inclined to complicate it further with things like morning stars and flails negate shield bonus.

    Again, I'm not really after realism but rather more tactical options/advantages for fighters compared to spell casters.

  19. My ideas for tactical options go a different route.

    Of course mine require minis or counters to play out and its more based on using strategy than multiple ways of figuring out which weapon can do what to which armor.

    (Note I plan on tweaking what I wrote in those things sooner or later. I've come up with some smoother options in a few cases, and a few bits I just think need to be either clearer or edited to be actually correct.)

    Fighters need to use tactics IMHO, not just having kewl powers.

    Though I guess if you wanted a quick and dirty weapon effect system you could go Cutting, Bashing, and Penalizing. (Obviously counting things like ranged, polearm, or normal.)

    (Bonuses are in general, not just against what's reduced.)
    Cutting gets improved damage but reduced to hit against any armored target.
    Bashing has improved chances to hit, but reduced damage.
    Penalizing does less damage and is hard to hit with, but causes lots of saving throw or attribute check type effects. (Stunning blackjacks, blocking attacks with a Sai or Main Gauche, tangling with Nets or Bolas.)

    Sure my idea is just generalizing things (An Axe, Sword, and Spear all hit and hurt differently after all!), but its a quick and dirty way to make different weapon types appealing. Technically an arrow is gonna have little trouble with most armor, but abstractly it could be affected, and its pointy bleedyness shouldn't be any stronger, but its a neat quick way of doing it.

    Do you have armor or something armor like? Ok, the most popular weapons have a harder time hitting you, but now they all do more damage. However, the mace and warhammer are gonna hit you more often, but in general aren't quite as deadly though it hurts. Penalizing weapons have a harder time causing actual hits and the damage is reduced, but they can SERIOUSLY mess you up.

    Wow. Imma adding these ideas to my actual house rules topics! I could make some use out of them with a little spit and polish!

  20. I'm a bit late to this but anyone who's interested might like to try my re-writing of the Weapon Vs Armour tables (assuming my broadband is actually working when you try to download it!):

    The system given there makes no difference to the chance to hit from the actual books, it just trys to lay the info out in better way.

    I've been using it for a while and it seems to be a good way of getting the armour mods into play while leaving enough "brain time" to also cope with speeds. With both rules in place, fighters do actually have something to think about when they pick their weapons.

  21. Captain Rufus I quite like your system, I may experiment with miniatures in my normally abstract combat systems as a consequence.

  22. Thanks! My blog has my whole pile of mods there. I used 2nd ed AD&D as a foundation, but its closer to BECMI/Moldvay/Cook/RC with 2nd ed classes and spells. And Gold Box AD&D game combat.