In Chapter Four of All Quiet on the Western Front, Paul describes the battle front as a "mysterious whirlpool."  The soldier walks along without thinking, suddenly he falls to the earth as a "storm" of shell fragments pass over him; yet, he does not remember hearing the shell or having thought about falling to the ground:

We march up, moody or good-tempered soldiers--we reach the zone where the front begins and become on the instant human animals.

Caught in this whirlpool in which animal instinct protects the soldiers, Paul finds himself again embroiled in warfare.  Because he is reunited with his companions, he volunteers to crawl into No Man's Land between the two enemy armies and learn the strength of the French. On his way back, however, Paul loses direction and when a bombardment begins, he huddles in a shell-hole.  But, he agonizes about his enemy jumping into this same hole. In anticipation of what can be a fatal turn of events, he prepares himself for his line of action:

If anyone jumps in here I will go for him.... stab him clean through the throat, so that he cannot call out; that's the only way; he will be as frightened as I am; when in terror we fall upon one another, then I must be first.

This "kill or be killed" is part of Paul's animal instinctiveness, his survival instinct.  This is what causes him to stab the Belgian soldier; however, as he sees that the soldier is yet alive, Paul recognizes the fact that this man could have been himself. Perhaps, Kropp's observation that each man, whether German or French, is in this war to protect his fatherland, so "Now who's in the right?" causes Paul's disquiet. Later, having found the man's name on his papers, Paul thinks of him as an individual like himself, a soldier defending his fatherland, and he feels remorse for his murderous act. But, if he were to have been this rational at the moment that the man entered the same shell-hole, Paul may have lost his own life. Clearly, this episode illustrates the dehumanizing effects of war.