If war is a necessary course of action, then it is possibly the most important lesson. War is of course the least desirable course of action. But his job isn't to find peace without war. His job is to do his job (win wars) if called upon. The people responsible for peace are the political leaders. If they fail, they turn to the military.

Yes, sometimes they turn to the military without exploring all avenues to peace. Whether or not those are good decisions can be long debated. But do not put the onus for peace on him. Rather, be thankful that he is capable to do his job. The responsibility for peace lays on the shoulders of political leaders and diplomats.

Quoting the only line that ever stuck with me from Alien vs. Predator:

"Why do you have a gun?"

"It's like a condom. I'd rather have it and not need it, than need it but not have it."