When Paul stabs this French soldier, he is already in a state of heightened tension and nerves, "strained to the upmost." As such, it is completely without thinking that he stabs the body that hurtles into the trench with him. He says "I make no decision," and after the stabbing, he "comes back to himself," as if the actual stabbing were committed in a sort of fugue state. Once he realizes what he has done, Paul is petrified that the noises the soldier makes, now mortally wounded but not dead, will betray him, but it does not occur to him to stab him again. He is too afraid to, and he wants only to get away. He cannot bear to listen to the sounds the man makes, but it is evident that the act of stabbing him is not one characteristic of Paul, and in his conscious state of mind, he cannot bring himself to replicate such an intimate and intense method of killing.

When he eventually crawls back over to the dying soldier, he is struck by the look in his eyes which he interprets as "a dreadful terror of death, of me." This causes Paul to whisper "no," not wanting to think of himself in such a way, as a person to be terrified of. He is guilt-stricken and decides he must help the soldier. Like this, he can see his face, his expressions, and his reactions to what Paul has done, and he wants to help the French soldier. Paul cannot cope with the fact that he has "killed with my hands," and is "close at hand" with someone "whose death is my doing." As such, his reaction is one of regret, fear, and a desire to undo what he has done.

It's the method of killing that's important here. Paul stabs the French soldier to death, a method of killing that establishes a more direct connection between the killer and his or her victim. Stabbing the French soldier brings home to Paul the full horror of what it means to kill someone. This isn't like dropping a bomb from a plane, where you can put some moral as well as physical distance between yourself and your victims. In a case of hand-to-hand combat such as this, you and you alone are responsible for your actions and their consequences.

Paul's guilt immediately kicks in, as well as his basic humanity, and he tries to do whatever he possibly can to save the French soldier's life. His feelings of guilt are further compounded when he discovers the young man's personal effects. These establish the dead man's identity, not as a Frenchman, not as an enemy combatant, but as a human being.

This particular section of the text can be found in Chapter Nine, where Paul is in No Man's Land and in the middle of a bombardment. Suddenly, an enemy soldier jumps into the same shell hole he is hiding in, and Paul quickly stabs him. However, he is agonised to discover that the man is not dead but is still barely alive. This is the first time Paul has killed a man in hand-to-hand combat, and it is clear that Paul is shocked by the responsibility he feels and the guilt he is burdened by. Note how he describes his emotions as he watches the French soldier gasping out each breath:

But every gasp lays my heart bare. This dying man has time with him, he has an invisible dagger with which he stabs me: Time and my thoughts.

The quote is important because it describes the impact of the French soldier and his suffering on Paul, and each breath is described as exposing Paul's emotions and filling him with horror. Paul is having to face the consequences of his actions, and because this is the first time he has killed anybody like this, it is much more difficult. In addition, note the use of the metaphor in the "invisible dagger." Even though it is Paul who has just stabbed the soldier, it is the soldier who is described as stabbing Paul as he is filled with guilt. This is why Paul does what he can to save the soldier, even though he knows he is fighting a losing battle.