Omaha Beach Scene from Saving Private Ryan.

In my bibliography of 1200 items, I can't recall a serious historian who theorizes warfare as a function of "male aggression."

The great military leader and theorist Sir John Hacket had it right: 

"The military makes demands which few other callings do. Emotionally disturbed people talk about being trained to kill.

"The whole essence of being a soldier is not to slay but to be slain. You offer yourself up to be slain, rather than setting yourself as a slayer. One can get into very deep water here, but there’s food for thought in it.”