Themes
(1) Lost Generation
Some of the recruits including Paul enlisted in the war right out of high school, not giving them any time to create a life without the war. Throughout the book those characters express a sense of loss. They have nothing to go to after the war. Any chance of them having a normal life afterwards was snatched away from them.
(2) War Dehumanizing
In the mist of the war the recruits became less and less human. Their alertness is heightened and their survival instincts kick in. They aren't thinking about what they are doing they just do it to stay alive. Paul automatically stabbing the Frenchman was not humanlike at all and you can see the contrast of that when he is forced to spend more time with the man and he comes to his sences.
(3) War Brings Out The Worst In People
Not only does war dehumanize the people making them do whatever and kill whoever to stay alive, it also feeds power into the otherwise powerless. Himelstoss, in everyday life, is a postman; powerless and just doing his job. In the war he is strict, arrogant and demanding. He treats his trainies horribly and demands respect without returning it. His taste of power brought the worst in him.
(4)War Brings Out The Best In People
In the war you have terror all around you. That makes you more appreciative and caring for the things and people around you. It bulit a comradeship between the men as Paul being nice to the Russians and helping the Frenchman as he died. War made him care by making him realize that death is within grasp.
(5)War Is Worse Than Death
The fear and anticipation of death is worse than death itself. During the war they see people, as well as their friends, suffer and die. They hear bullets whiz by their ears and feel the heat of a near by explosion. In the end Paul died with a smile on his face and they said that he was probably glad that it was over. They are scared of dying but going through all of that and having to live with that afterwards is more painful than merely dying.