Tactics: In war film battle scene everyone always has someone to fight
You see these big battle happen and they all run to each other and start fighting with swords and shield
So what you should do in this situation, you have these few guys arrive late to battle, and they walk in the side and just start to stab people in their back who are already fighting
I was thinking about genghisKhan who win nearly all fights and I think this was his tactic