War destroys the young before it kills them
Paul and his classmates are teenagers when they enlist. The war doesn't just put them in danger — it takes away their ability to grow into adults. By the time Paul dies, he has no plans, no desires, no sense of a future. The novel argues that this psychological destruction is as complete as any physical wound.
The gap between propaganda and reality
Kantorek's speeches and the patriotic pressure that sends Paul to war have nothing to do with what the trenches actually are. That gap drives the novel. Every scene at the front is an implicit answer to the speeches Paul heard in school.
Comradeship as the only surviving value
Paul doesn't fight for Germany or for any idea. He fights to keep his friends alive. The bonds between soldiers, especially between Paul and Kat, are the only thing the war hasn't managed to corrupt. When Kat dies, Paul has nothing left to hold onto.
The impossibility of return
Paul's leave makes clear that surviving the war doesn't mean you can go back to who you were. The civilian world and the trench world are incompatible. Paul is a stranger at home and only recognizable to himself at the front. That's not freedom — it's a different kind of trap.
Death as bureaucratic and random
Remarque refuses to make deaths meaningful or heroic. Kemmerich dies from an infection. Kat dies from a second wound while Paul is already trying to save him. Paul dies on a quiet day. The randomness is the point. The war doesn't distribute death according to who deserves it.