“The Things They Carried” by Tim O'Brien deals with the responsibility, remorse, and the isolation and loneliness soldiers went through the war of Vietnam, chiefly due to the emotional immaturity of the soldiers.
It is not surprising as many of the veteran soldiers who have participated in wars suffer from its lingering psychological and emotional effects; especially when they had to kill the other human beings or see the things they were not psychologically grown-up enough to reasonably judge.