World leaders who make war tend to have a particular personality profile called “high need for power”. American presidents who show this are, throughout history, more likely to take their countries into war than those who don’t. Dwight Eisenhower didn’t show it for instance, while George W Bush did.
“Need for power” was identified by the great psychologist David McLelland as one of three basic, largely unconscious drives, which motivate people to different degrees. The need for power—the others are the needs for affiliation and achievement—is where you are motivated to dominate and control what other people want, need or fear.
In simulations of the Cuban missile crisis where nuclear holocaust between Russia and USA was narrowly averted, people who are high in the need for power acting the role of war room decision makers tend to take actions which would, in 1962, have resulted in nuclear war.
All leaders need to have a certain appetite for power—leadership is too stressful otherwise, and power’s effects on the brain’s act as a sort of anti-depressant. But like all addictive drugs, too much for too long causes dangerous changes in the brain, which include reckless disinhibition, risk-blindness and difficulty in seeing things from other’s perspective: ex UK Foreign Secretary Lord David Owen has described this as the “Hubris Syndrome” which he diagnosed leaders Margaret Thatcher, Tony Blair and George W Bush, among others, as showing.