Paul Lazzaro is a vengeful and mean-spirited soldier who is taken as a prisoner of war alongside Billy Pilgrim. He befriends the dying Roland Weary, promising that he will one day avenge Weary’s death by assassinating Billy. Paul is small and thin, and when he tries to sneak cigarettes from one of the Englishmen at the POW camp, the man breaks his arm, not realizing how fragile Paul is. Juxtaposed with Paul’s small stature is his large penchant for violence. He’s obsessed with revenge fantasies. In his relatively powerless and pathetic situation as a POW, these fantasies are the only way he can assert his own significance and power over other men. By cooking up incredulous assassination schemes for those he perceives to have wronged him, he convinces himself that he is a powerful person, and that this will become apparent to everyone one day, even if they currently view him as non-threatening.
However, Billy is in fact assassinated decades after WWII by Paul Lazzaro, so it seems that Paul actually made true on his unbelievable promise. In a symbolic sense, Paul is a manifestation of the concept that survivors never truly escape the war, and that the horrors they endured will haunt and follow them throughout their lives. Additionally, Paul’s assassination of Billy is one of many examples in Slaughterhouse-Five that prove how pervasive needless, wasteful violence is in human society.