I'm moving away from thinking about how to use Chaimail as the OD&D combat engine. Chaimail and OD&D just have too many disparities between them to really synthesize them in a way that is true to the word of each ruleset, although the opinion of the reader may vary from my own. Instead, I've been taking aspects of Chainmail and D&D and rebuilding them from the ground up.
How did this all start? When I was working Swashbuckler! yesterday, I noticed that many of my sword fighting mechanics could be easily ported into, and were like inspired by, Chainmail. I'm not quite ready to talk too much about swashbuckler yet, so I'll discuss my Chainmail/D&D fusion experiment instead. Keep in mind, however, that I am not attempting to unitize whole (or even partial) pieces of either the Chainmail or D&D rulesets.
Each character and creature fights as a number of men. Player characters, for example, fight as a number of men equal to their level. Rather than having separate attackers and defenders, creatures engaged in melee attack simultaneously. In a two person combat, each combatant rolls a number of d6s equal to his or her fighting capability (equal the number of men he or she fights as). Successful rolls are determined (depending on troop type) and the number of successes are compared. the combatant with the greater number of successful rolls is the victory and slays his or her opponent.
Depending on a combatant's troop type, he may gain certain advantages over his opponents. Take a a light footman fighting an armored footman for instance. For each single success, the light footman needs three if his attack dice to roll 6s. On the other hand, the armored footman's need to roll a 4 or higher for a roll to be considered a single success. Thus, a single light footman with a fighting capability of 1 man cannot defeat an armor footman of the fighting capability. Even three light footmen have a difficult time taking on a single armored footman.
Now, I'm considering some sort of critical hit table rather than instant death. But for the time being, this is mostly a brainstorming exercise, although it might very well turn into something more.
The Fantasy Combat Table allows characters to take on mythical creatures with a slightly higher chance of success than when using the basic combat rules. Each combatant rolls 2d6 and compares it to the fantasy combat table. If one combatant succeeds his or her roll while the other does not, the successful combatant slays his or her foe. Otherwise the combat continues into the next round. Neither combatant's troop type is factored into the combat table. Only heroes (4th level and higher characters) may roll on the Fantasy Combat Table.
Fighters attack and defend as Armored. After reaching hero level, fighters always have the option of rolling on the Fantasy Combat Table.
Thieves attack and defend as Light. When attack unnoticed from behind, thieves throw 1 additional die from 1st to 3rd level. They throw 2 additional dice from 4th through 7th level, and 3 additional dice from 8th to 12th level. Only when backstabbing, does a thief have the option of rolling on the Fantasy Combat Table and only after reach hero level. (Note that thieves also possess increased chances to hide, move silently, pick locks etc.)
Wizards attack and defend as Light. Starting at 1st level, wizards are able to cast spells. The maximum [complexity or level] of a spell a wizard is able to cast is equal to half his level, rounded up. Wizards may never roll on the fantasy combat table.
Clerics attack and defend as Heavy. They are able to turn units worth of undead creatures. Starting at 2nd level, clerics are able to cast spells. The maximum [complexity or level] of a spell a cleric is able to cast is equal to half his level, rounded down. Only against undead, demons, and other unholy creatures and having reached hero level may clerics opt to roll on the fantasy combat table.