By Jean Froissart - From Chapter CXXIX of Jean Froissart's Chronicles, example source at http://www.maisonstclaire.org/resources/chronicles/froissart/book_1/ch_126-150/fc_b1_chap129.html, Public Domain, Link.
I've always been a sucker for mass combats in D&D I blame the H1: Bloodstone Pass adventure, with it's Seven Samurai plot and grand battles .
I like the compact stat block: Light Infantry Cost 4, MV 12, AH 4, HD 1
- Cost: Each month, pay 10 gp times the cost per figure in the unit. A figure likely represents 10 people.
- MV: On the miniatures field, may move that many inches (an inch is assumed to be 20 feet)
- AH: Each attacking figure rolls a d6 per attack. On the AH (eg. Armor Hit) or higher it does one HD of damage.
- HD: The number of hits a figure can take.
As expected, there are rules for morale, movement, and terrain. Nothing too complicated.
I haven't used “Book of War”, but I thought I'd raise attention to another option.