Vonnegut was deployed to Europe to fight in World War II, and was captured by the Germans during the Battle of the Bulge. He was interned in Dresden and survived the Allied bombing of the city by taking refuge in a meat locker of the slaughterhouse where he was imprisoned. This event inspired his novel, Slaughterhouse Five. It made him develop nihilistic views considering the tragedies he witnessed. Also, he had major family tragedies - mother's suicide and father's alcoholism (I believe). Research that.