Stanhope - He is unhappy and angered that Hibbert is trying to escape from the Front Line, right before the German attack. Although he pretends to be ruthless, and says that he will shoot Hibbert for deserting. It seems more likely that this is an empty threat and that he doesn't want to kill Hibbert, just frighten him into choosing what Stanhope thinks is right.
Hibbert - He is shocked that something that he thought would be so simple, going to see the doctor, is being so hard. He is outraged that Stanhope is stopping him and is reckless due to his emotional state (hitting Stanhope). He is terrified and deeply unhappy in the trenches which is revealed later on, and doesn't think he could take the big German attack.
