Can you play 'rally cry' just before counting strength at the end of a battle?

monk said:

Yes, and any units routed in the battle will be unrouted. In fact, that's often when it gets played

However, note that if there are any units that were routed BEFORE the battle will not enter the battle at this point; all units that enter the battle must do so at the beginning of the battle. Only units that were already in the battle (and routed during the battle) will count for strength at the end.