why has Himmelstoss changed his attitude

Second Company is taken to a field depot for reinforcements, and the men are given some time off. Himmelstoss wants to make amends with the boys, and Paul is willing to forgive him, since Himmelstoss helped Haie when he was hit in the back. Even Tjaden comes around when Himmelstoss becomes the new sergeant-cook and treats the men to delicacies.

He realizes how horrible the war is and what the boys have been through.