That's a pretty broad question, but fortunately there are many examples that you can use to illustrate your ideas. I'll offer a few.
One of the classic war novels is All Quiet on the Western Front. This was written by German author Erich Remarque. It was set during World War I and caused quite a stir among the Nazis in Germany a few years later. They banned the book and even denied that the writer was German at all. What makes this book great is that it does absolutely nothing to promote the “glory of war” that we so often see in other works. It simply shows that war destroys people’s lives.
Another controversial war novel was Johnny Got His Gun by Dalton Trumbo. This novel showed the devastation of war by focusing on one character who lost all four limbs as well as his sight and hearing. Trumbo was blacklisted by Hollywood during the anti-communist witch hunts that went on in the fifties in America.
As for movies, one of the best in the anti-war genre is Full Metal Jacket, directed by Stanley Kubrick. This film shows the psychological breakdown that can occur in wartime among soldiers. Platoon is another good one, although its antagonist is more "evil" than war addled.