Mass Combat
Here are some rules for mass combat. This is not intended to be a full miniatures war game, but rather rules that will be quick, easy, and hopefully fun. (Adapted from War of the River Kings, Paizo Kingmaker AP). Below we describe how to build an army, this page says how armies fight.
An Army
Before you can have a mass combat, you need some armies. The stats for an army are below or you can use the Sample Armies.
Name: Duh
CR: Take the CR of the underlying creature and adjust by size. A resulting CR of less than 1 doesn't count. Make it bigger.
Size: Number of units in the army
hp: CR x Average hit points for the hit dice type (3.5 for d6 HD, 4.5 for d8, 5.5 for d10, and 6.5 for d12). Drop fractions.
DV: Defensive Value, like AC. 10 + Armies CR
OV: Offensive Value, like BAB. Equal to Armies CR
Tactics and Resources: Things an army gains with experience
Speed: # of 12 mile hexes the army can cover in a day.
Morale: From -4 to +4. New army starts at 0.
Consumption: The cost to the kingdom PER WEEK for the army
Leader: Who leads the army and their CHA modifier
Tactics
If an army wins a battle, you attempt a Loyalty check against the kingdom's DC. If you succeed, the army learns a new tactic. An army can know a number of tactics up to it's half of it's CR. Some tactics:
Resources
Resources are a 1 time cost (in BPs) for the army. Some sample Resources:
Special Abilities
Some armies have special abilities, like breath weapons. Mostly for monsters I think.