What is important about the line at the end of the section describing Kat's death-"Then I know nothing more"?All Quet on the Western Front by Erich...

Although the war is near its end, Germany continues to
fight even though there is no hope of winning.  The men feel as though they are
prisoners sentenced to death; they fight at the front, then they wait to fight again. 
Paul has a sense of things falling apart as Detering finds a cherry tree and takes a
branch with him as he heads home, going AWOL.  Another soldier, Berger, jumps out of the
foxhole to save a dog and is killed; Mueller is shot in the stomach and takes a half an
hour to die.  Everthing is "heroic and banal" Paul
remarks.

Left with only Kat, who has been hit in the shin
while bringing food, Paul must carry him to a dressing station because he bleeds too
much. As he stops to rest, Paul talks to his dear friend, exchanging
addresses.

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Kat my friend, Kat with the drooping shoulders,
and the poor, thin moustache. Kat with whom I know as no other man, Kat with whom I
shared these years--it is impossible that perhaps I shall not see Kat
again.

Sadly, on the last leg
of the trek to the dressing station, Kat has caught a splinter in the back of his head
and is dead when they arrive.  Paul is incredulous; he feels hopelessly bereft without
his friend.  As he looks around "all is as usual," but all is really not.  Without Kat
to share with, to talk with, Paul has no one by whom to measure himself, to keep himself
sane:  "Then I know nothing more," he narrates.  Nothing has meaning without his
friend.  At this point, Paul may also have fainted as the impact of losing his friend
has put all into a state of senselessness and in his fatigue and grief he loses
consciousness.