Quote 1
There were thousands of Kantoreks, all of whom were convinced that there was only one way of doing well, and that way theirs. And that is just why they let us down so badly. (1.47)
Clothes do not make the man. Most of the authority figures in the novel are painted as one form or another of idiots, sycophants, toadies, and other lower order life forms. Kantorek and Himmelstoss are core figureheads in this arena. But they represent the many others who assume their form. This type of representation is one of the things that makes All Quiet on the Western Front such a great book – it is clearly everyman's story of the war. Think about it: there is nothing particularly special about Paul, other than that he wrote this book. His story is presumably played out thousands of times, just as the passively evil Kantorek and Himmelstoss's stories are repeated many times, in many locales, all around the war effort.
Quote 2
We march up, moody or good-tempered soldiers – we reach the zone where the front begins and become on the instant human animals. (2.27)
Many quotes like this pepper the book. There is a conversion that happens when the danger, or kill-zone, line is crossed. Paul sheds his soft, gentle, listening self and adopts a killing, shouting, aggressive demeanor which he continually links to that of a hungry or wounded animal. His identity thus goes back and forth between these two faces.
Quote 3
I imagined leave would be different from this. Indeed, it was different a year ago. It is I of course that have changed in the interval. There lies a gulf between that time and to-day. At that time I still knew nothing about the war, we had only been in quiet sectors. But now I see that I have been crushed without knowing it. I find I do not belong here any more, it is a foreign world. (7.173)
In what ways has Paul been crushed? In light of all of the gruesome circumstances he's had to weather, Paul seems like one tough cookie to us. Then again, we don't really get to meet him until he's already elbow deep in wartime responsibilities. We don't know what Paul was like before the war.