Zimmerman Syndrome
The pattern of behavior which erupts after a person has shot another to death in cold blood, marked by anger, denial, specious justifications, depression, copious hand-washing, paranoia, avoiding public exposure, etc... and perhaps even several attempts at an apology. Often resulting in the abuse of highly addictive pain-killing drugs and ending in attempts at suicide.
These soldiers returning home from an unpopular foreign campaign are likely to suffer severe Zimmerman Syndrome when the adrenaline wears off and they realize they killed a lot of innocent people along the way to their goal.