Ackshually, bloodbaths were rare in ancient warfare. The losing side will often break and flee before being slaughtered. The winners usually let the enemy flee because the risk of getting injured (pre-antibiotics) AND the LOOT. Soldiers join up for the loot (and pillage, and rape). It is one of the few ways a commoner can get rich quickly. Fleeing armies often throw away their weapons, armor and baggage trains. Everyone will then return to their villages and go back to being farmers until the next warring season, maybe under a new flag.