Welcome aboard Alcibiades, interesting stuff.
I suppose in time of war the definition of psychopath can become much looser, even a positive characteristic in many situations.
Being understandably cautious (never having studied it) about what a psychopath specifically is, I'd tentatively suggest Patton.
As another
possibility, while I'm far from convinced this man was a Psychopath he certainly exhibited much 'eccentric' behaviour that did his military career no harm at all:
Fighting Jack Churchill.
Mad Jack Churchill
Dirlewanger would fit the psychopath or sociopath mould, certainly a total lack of conscience was present, but I don't think it had that much bearing on his military career... seems to me he would most likely have behaved in broadly the same criminal manner whether there was a war or not. Though you don't appear to be looking so much for the maniacal murderers of the period (who perhaps perpetuate the 'skewed' popular view of the mindset?), more those who exhibited more subtle signs?
Cheers,
Adam.