From Longsword Games
PDF – Free
This is a system designed for small battles with 40-60 figures a side, and micro-management of individual combats. It's rank-and-flank, but units are malleable, and are to gain figures, change the number of columns or ranks, have combinations of two types of infantry or cavalry (for instance, bow-and-bill, or bill-and-men-at-arms).
It can be played on a fairly small table, requiring a fairly minimal amount of terrain.