[ZenGum]

I think the laws of war are a bit more than Bruce says. They give soldiers at least some guidelines about how they should act, and prevent it from becoming an anything-goes situation.

In a conventional, symmetrical war (eg WWI, WWII, Korea) there were cases of both sides limiting their behaviour. In WWI, the use of notched bayonets was stopped by mutual agreement.

The treatment of prisoners is another area where captors - who could have just slaughtered them, or starved them to death - have behaved ... well, better than the worst they could have done. These rules make surrendering a viable option on the battlefield, which does slightly improve the humanity of the overall situation.