Descending Armor Class is Silly

Why do all of the OSR games I’ve looked at insist on sticking with descending armor values? Ascending armor value is an easy and intuitive change. It just makes sense in a system where you roll a d20 versus a target number to hit. This is the best thing to come out of third edition, in my opinion. Is this insistence on descending armor class mainly a compatibility concern, aimed at keeping the rules consistent with previously published material? I have to assume this is the reason, but I don’t know if it’s a good enough reason. Most old school gamers love charts and tables, and a couple of “AC Conversion Charts” would straighten out the compatibility issues. Anyone who can calculate the THAC0 of a 9th level cleric in their head can figure out how to change AC 4 to 15 on the fly.


9 thoughts on “Descending Armor Class is Silly

  1. Hear, hear. I’d rather memorize equipment charts and spell lists than THAC0 tables. I mean, if the choice is between basic math and memorization? I’ll take basic math.


    1. In 1st edition we didn’t do any math, we just looked at the table. All the To Hit tables were on one page of the DMG, so it was fast and easy.

      Though the ascending AC that Lamentations of the Flame Princess uses is even easier.


    Actually, I’m good either way. I have never found a source on why AC is descending in early editions of D&D, beyond the coolness factor of having a negative.

    We use Lamentation of the Flame Princess for our D&D fix and it uses ascending, but I don’t have a strong feeling either way. If I had to pick one, I’d go with ascending too, for exactly the reasons you listed.

  3. As someone who cut his teeth on 3.5e and then got fascinated with the OSR I’ve wondered this myself. But then, I confess that I find 3e to be much more streamlined in many more areas – using a D20 system as opposed to random dice for different task, uniform experience tables, etc. From an outsider perspective it sort of seems like the reason people stick with this system has more to do with familiarity and nostalgia than actual efficiency. But I’m open to being shown wrong on this.

    1. After having had the opportunity to play every major edition of D&D from 1e to 5e, I think it’s fair to say the first three iterations of the game steadily accumulated more and more complex rules without *necessarily* becoming a better game at the same time.

      3e cut a lot of the rules bloat from 2e (though I think some of this was a result of it having only half the original lifespan of 2e), and 4e saw even *more* streamlining over 3e — where the game peaked in sheer number of “lateral” character options.

      I think a “return” to faster and simpler play is preferable to 3e/4e, but from what I’ve seen of 5e so far… they’ve overshot… and will probably land somewhere in the region of “not enough to do…”


      1. You bring up some good points Dither. I think there may be more than one thing that could be meant by “streamlined” here so this warrants a bit more of a fine grained analysis. By “Streamlined” one might mean the following:

        1. A robust rule-set apparatus;
        2. A rule-set aiming at faithfully modelling reality;
        3. A rule-set that is simple;
        4. A rule-set that is quick and easy to implement;

        From what I’ve seen, the Original 1974 game seamed to be none of these things (some might argue that it was quick and easy to implement but to my mind the amount of interpretation and house-ruling required to play the game belies this claim).

        The Holmes edition, B/X, BECMI and the Rules Cyclopedia each improved the original game but in different ways. Holmes and Moldvay both attempted to make the game simpler and easy to implement so as to allow new players to learn the game quickly. Mentzer did the same, but with each new expansion of the BECMI the rules-set apparatus became ever more robust in attempt to model real-world scenarios (e.g. naval combat and mass combat) in an RPG environment. This modularity allowed one to choose their preferred level of complexity Increased complexity however came at the expense of ease of implementation: the rules were spread out over a wide range of documents making quick reference difficult. The Rules Cyclopedia attempted to organize the BECMI material into a single reference document, thus solving the ease of reference problem. However it was no longer a simple system,

        AD&D was robust from the get-go. It is not a simple system, nor (arguably) are its rules, if played the way they are written, always quick and easy to implement (a case in point is Gygax’s original rule on initiative). AD&D added further complexity and attempted to more faithfully model the real world (different weapon speeds, different weapon damage, non-weapon proficiencies etc). However many feel that the result was cumbersome mess.

        Third edition kept much (though not all) of the robust apparatus of 2e, but cleaned it up and created a core mechanic (the D20 system) which both faithfully modeled the real world and vastly simplified the game. It is still much more complex than say the Red Box game. For that reason it is not as easy to learn and implement. Nor was the game (at least where combat was concerned) quick to play.

        Fourth edition tried to further simplify the game and make it easy to learn to play, though many, myself included, feel that the changes that were made lead to a homogenization of the character classes and came at the expense of faithfully modelling the real world. Also, combat still took far too long.

        I only play-tested 5e for the first few months so I don’t know what the current state of the game looks like. I know that they strove to simplify things even more to allow the game to both be easy to understand and quick to play (aiming at the last two senses of “streamlined” mentioned above). However to my mind the game did not do nearly as good a job as 3e when it came to faithfully modelling the real world.

        An edition that is robust enough to accurately model many real world phenomena, but that is also simple to learn, easy to reference and plays quickly at the table would indeed be an accomplishment. Thus far I haven’t seen it.

  4. Yea have to agree, my first experience was 2nd edition I never DM’d back then I barely understood THACO (just let the DM do the work) and descending AC was just the way it was. I can’t imaging even wanting to go back to that system 3.5e all the way.

  5. I suspect nostalgia is a huge driving force in its persistence. It was the first system. While it is mentally counter intuitive (seriously, why did it take 2 decades to invent ascending armor class?), there is always a certain safety in the familiar.

    There’s a sort of tacit admission as to how bad the system is with the retroclone Swords & Wizardry. That system actually supports both ascending and descending armor class. In fact, you can publish your own modules and there are only two terms: You have to give some credit to the original S&W group AND you must list all armor class in both ascending and descending terms. Can’t do just one.

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