Slaughterhouse-Five is about a very particular experience of war. This book isn't about officers or heroes. It's about privates, most of whom don't want to be – and shouldn't be – on the battlefield. And it's about prisoners of war, men who have been deprived of any kind of control over where they go and what they do. There is nothing romantic about war in Slaughterhouse-Five. In fact, the villains of the novel are the ones who continue to romanticize violence and killing, men like Bertram Copeland Rumfoord and even foolish Roland Weary.
By giving villainous characters like Roland Weary and Bertram Copeland Rumfoord a love of war (or the idea of war, at least), Vonnegut conveys his strongly anti-war sentiments to the reader.
By avoiding representations of the battlefield and focusing instead on prisoners of war, Vonnegut draws the reader's attention not to war itself, but to the suffering it causes.