For Christmas I asked for and got a book written by a CIA psych guy who analyzed the personality of world leaders. It was his job.
Right out of DSM-IV, the first choice for world leader (and what politician does not want to be one?) was narcissistic, the second obsessive and third (but not in an open society), paranoid.
Once you know what to look for, I realize I have already met many people in each of these categories of Personality Disorders. Coworkers, party guests, bosses, etc..
If it is a contest between putting a tiny dent in a politician's vanity and soldiers dying, how many must die? (Hint: to put an upper bound on the answer, there are about 6^9 people in the world).
Vanity trumps almost everything.
E = IR, and Power + vanity = bad things for everyone else.