Here's how a priest or bishop in BattleMaster leads troops into battle:
1) Change class to a warrior.
2) Hire a unit.
3) Lead them into battle.
4) When you want to stop leading troops into battle, leave the unit as militia and change class back to a priest.
You don't have to change your character's basic drives and desires to "I fight wars all the time now! I am big burly fighting-type man!" to change their class from priest to warrior. You just can't lead troops into battle while preaching to the peasants, or while getting the game-mechanic benefits of priest-type travel.
