1. Warfare is dehumanizing and causes loss of purpose
Paul struggles with many things throughout the war, including finding his purpose. He loses sight of all of his goals and anything that doesn't involve the war. He recognizes that the was has just become young people fighting each other for no reason. "We loved our country as much as they; we went courageously into every action; but also we distinguished the false from the true, we had suddenly learned to see. And we saw that there was nothing of their world left."
2. Enemies who are struggling to survive can be helped
Paul understands the soldiers on the other side of the fight have lives and humanity too. When he sees Russian soldiers suffering in a German prison camp, he decides to share his food and cigarettes with them. Paul understands that these soldiers have lives outside of the war, and they are fighting to survive. He didn't have to share with his enemy, but he chose to. This proves his humanity has not been taken away and furthers his questions about the purpose of war.
3. The amount of death in warfare goes unnoticed too often
Throughout the duration of All Quiet on the Western Front, several soldiers are lost, on both sides of the field. Paul ends up being the one and only left from his original company. The leaders of the fighting countries don't know the horrors and pain that the soldiers faced. This trend continues in real life, as the same countries are the ones that also started World War II.