So, as you probably know, I’ve been tinkering with mass combat as of late, and thinking about how it might best be approached for my own campaign (and ADD). I’m particularly drawn to the basic idea of the old Swords and Spells supplement (the last supplement published for 0E, unless you count it as a game unto itself, which is at least implied by the booklet itself). The concept is to simply “scale up” the D&D combat system, using the averages and probabilities to determine damage without rolling dice. There is nothing to say this concept wouldn’t work exactly as well with the AD&D combat system.
For example, take the D&D equivalent of the Stamford Bridge; 1 lord (let’s call him 10th level, AC 0, 50 hit points, with a long sword +2) facing off against 100 orcs. If you go by the averages, the 10th level fighter loses that battle.
The orcs hit 5% of the time (20 on a d20), and let’s be kind and say only 3 of them can attack the lord at any given time. The lord hits 80% of the time (4 or better vs. AC 6). The orcs do an average of 5 hp when they hit, while the lord pretty much kills what he’s aiming at. So, he kills 8 orcs per turn, while the orcs do 8 hp per turn. Bearing in mind that it’s a little fuzzy because of fractions and such (and doubtless eyes are already glazing over with all the numbers as it is), the orcs will eventually kill their man on turn 7, while the lord will run out of orcs to kill on turn 13. (There are only about a third of the orcs left, an impressive tally to be sure, but that’s more than enough left to make a drinking cup out of the lord’s skull to present to their chief.)
Nothing says you couldn’t apply these principles across the board. Voilà! You have a scalable version of AD&D combat, with a meaningful way of measuring damage between vastly different scaled forces. If the combat tables are built properly, you can even build in the weapon vs. armor type adjustments without having to resort to a separate table. The hard part is working up those average damage tables, and that’s not all that hard, really.
Now, what about lower-level characters? I’ve got something for them, too, that gives them meaningful input into large-scale battles without being given make-work jobs as scouts, monster-killers, or off on their own “defending the one critical hill that will mean victory or defeat for the entire army”. But that will come in good time.