From the Design Analysis Archives at John Kim's site:
https://www.darkshire.net/jhkim/rpg/sys ... cellaneous
Mass Combat:
a few systems include a mass combat system for quickly resolving large numbers of enemies e.g. Basic D&D’s War Machine rules, or the system in “Under the Moons of Zoon”.
If abstract such games may give an army damage based off its size (# troops) and perhaps a random variable with a leader strategy modifier and resolve over a number of rounds, or a really abstract method might just be a few random rolls on tables to determine victory/defeat (e.g. in the Central Casting character background generator books).
At the very detailed level, figures may represent “squads” and be played out with something like 3.0 D&D’s Complete Miniatures’ Handbook rules, or the wargame of your choice.
People have also suggested using the Swarm rules for things like e.g. Orcs in 3.x/4E D&D.
Savage Worlds again is designed for handling large numbers of creatures as part of its regular combat system (monsters are “up, down [shaken], or off the table”), and multiple checks for large numbers of NPCs can be rolled easily e.g. 10 guys shooting arrows might have Shooting d6 each, and so 10d6 can be rolled to find hits – handy for something like pirate ship battles).
Tunnels and Trolls or (I believe) “Forward – to Adventure!” use side-by-side battle systems and so also can resolve large combats fairly quickly.
Using the normal combat procedures for some games, multiple rolls of e.g. d20 can theoretically be streamlined using tables: Dragon Magazine #113 includes a fast-rolling table for D&D hit rolls/saves, where a single d100 roll generates the equivalent number of hits/misses as rolling 20d20 at a given target number.
However, this can’t easily determine # of crits/fumbles, only hits/misses.
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