Once the odds are determined, both sides make opposed Knowledge (Battle) rolls, modified by any of the circumstances below:
Casualties: Each success and raise causes the other side to lose one token. Casualties are generally distributed evenly throughout the force.
Morale: Each round in which an army loses a token, its leader must check morale. This is a Spirit roll modified by the circumstances below. With a success, the army fights on and both sides make another Knowledge (Battle) roll as described above.
Failure means the army is defeated but the troops conduct an orderly retreat. Make one more Battle Roll and then end the fight. (A leader may voluntarily choose this option as well.)
On a result of 1 or less, the troops rout and the battle is over immediately.
Savage Worlds Deluxe Edition p. 106