O'Brien claims that The Things They Carried isn't about war, it's about peace, but let's face it: the book is mainly set in a war zone during the Vietnam War. Peace stands out in relief against the war as we read. The warfare in the book isn't about tactics or violence or heroics. War is made up of boredom interspersed with moments of sheer terror. Other than that, it's mainly the backdrop against which the soldiers live their lives. As a backdrop, it can be horrible and gory, or it can be exhilarating and funny. O'Brien emphasizes that it's impossible to make generalizations about what war "is."
In The Things They Carried, the Vietnam War is a thing of horror that has made American decency twisted and dirty, a mockery of what it once was.
By refusing to generalize about war, O'Brien enriches civilians' understanding of it, pushing us to think beyond such trite sayings as "war is hell."