A distinction is drawn between the aggression of combat soldiers reacting adaptively to situations of real danger and a type of combat aggression that is personally motivated by a quest for revenge. In contrast to the adaptive aggression that posed few postcombat difficulties, the latter type of aggression resulted in regressive ego (and superego) functioning and led to uncontrolled rages, combat atrocities, and postcombat difficulties in the handling of hostility and aggression.
This latter type of aggression was traced to narcissistic injuries and subsequent narcissistic rage, often the consequence of the death of a combat buddy (loss of a mirror relationship).
Fox RP. Narcissistic Rage and the Problem of Combat Aggression. Arch Gen Psychiatry. 1974;31(6):807-811. doi:10.1001/archpsyc.1974.01760180047006