chainmail's weapon statistics for od&d's alternate combat system

by the end of this, i promise you'll have something useful! first, here is a cleaned up version of the one-on-one combat matrix for chainmail from my upcoming remake of the original 1974 dungeon game, fantastic medieval campaigns!

just wanted to show how that page is going to look. here's what i actually made today, the same data in an excel spreadsheet because i wanted to derive the AC values from od&d's "alternate" combat system by close-reading the one-on-one matrix from chainmail. i'm ignoring the values to hit cavalry because i'm not really worried about those tbh.

according to dmdavid's blog post on the origin of the od&d combat system (link), gygax made the following changes from arneson's original system derived from gygax's own chainmail (the only difference between arneson's system and chainmail was there being hit points):

1. "hit points became less realistic and more fun" (dmdavid's wording)
2. to-hit rolls switched from 2d6 to d20 (to sell more dice?)
3. AC values were flipped from ascending to descending

this post looks at points 2 and 3 from a mathematical perspective. first, we can simply flip the AC values given from chainmail by subtracting each given score from 14 such that 12 becomes 2 and 5 becomes 9. this preserves the likelihood of meeting each score, except that instead of rolling high you roll low.

oh, isn't that interesting? it looks pretty similar to the armor class values from od&d's "alternate" system! the most useful application of this is that you can use these scores from 9 to 2 instead of AC when rolling to-hit in od&d. for example, instead of using the AC descriptions on the table below, cross those out and refer instead to a table like the one above.

thus when a level 5 fighter attempts to hit someone with plate armor while wielding a flail, they refer to a to-hit score of 8. by treating this score of 8 as an AC value using the od&d table, we see that the fighter must roll 9+ on a d20 to successfully land a hit.

this would probably go well with the target 20 rule (link) by delta's d&d hotspot! but really i think the easier solution would just be to use the original 2d6 scores so you're not consulting more than one table. nevertheless, either solution is more interesting to me than the simple alternative system od&d offers (and which has since become 'the' d&d resolution system for combat) because it actually does take into account the types of weapons and armor used.

that being said, if you wanted a simplified version of the chainmail table, i've written about that a couple of weeks ago (link)! nothing wrong with a table, though; it might even be preferable to keeping track of all those weapon-specific attributes. that's why having a referee is nice, they can read the table for you!

now let me similarly convert the fantastic unit chart from the fantasy supplement of chainmail:

since these descending scores range from 12 to 2 (just as the ascending ones ranged from 2 to 12), it seems that this table probably was not the basis of od&d combat in any capacity the way that the regular one-on-one table was.

anyway, here's a table that combines the above chainmail data with the d20 mechanism from od&d, including bonuses for fighters! keep in mind that clerics improve every 4 levels, and magic users every 5 levels, whereas fighters improve every 3 levels: