Sergeant Himmelstoss is a perfectly nice guy on his own—he's your typical jolly postman. But slap a uniform on him and tell him he has free rein over a group of people and watch him transform into a grade-A jerk.
All Pain, No Gain
Himmelstoss represents the military complex during World War I. His job is to take young men, strip them of their individuality, and make them uniform (and uniformed) soldiers.
In his own words,
"You're going to be soldiers, and that's all!"
This would be bad enough (shades of Full Metal Jacket's Sgt. Hartman), but unfortunately he isn't very good at his job. His training playbook consists of performing marching drills and mud crawls.
If the squad doesn't sing loud enough for his liking, he makes them crawl through the mud until they sing like baritone birds. When the commanding officer orders the men to take leave, Himmelstoss makes them crawl through the mud again, wrecking their leave just because he has the power to.
Now, obviously the film had to cut some of his training for pacing's sake, but it remains evident that Himmelstoss does not properly prepare Paul and his friends for war. For example, Kat has to teach the young soldiers the basics on their first night stringing barbed wire.
The reason for this disregard is that Himmelstoss isn't interested in the young men under his tutelage. He obsesses over rank and status, and his teaching has more to do with ensuring his orders get followed than with instructing young soldiers on how to survive.
Given this, Himmelstoss represents a dark view of the era's military establishments—All Quiet on the Western Front sees them not as designed to defend their countries, but as institutions that use young men to obtain power and status.
Practice What You Preach
Eventually Himmelstoss is sent to the Front to fight alongside the 2nd Company, and we see his obsession with status again. Only at the Front, it's your ability to fight and survive that earns respect, not your rank.
And Himmelstoss doesn't like this one bit.
PAUL: It isn't customary to ask for salutes here. But I'll tell you what we'll do. We're going to attack a town that we tried to take once before. Many killed and many wounded. It was great fun. This time you're going with us. If any of us stops a bullet, before we die, we're going to come to you, click our heels together and ask stiffly, "Please, Sergeant Himmelstoss, may we go?"
HIMMELSTOSS: You'll…You'll pay for this, you… [He leaves.]
The attack begins soon afterward, and we see an interesting wrinkle in Himmelstoss's character. At first, he hides in a crater and refuses to advance. Paul hits him and berates him for being a coward, but Himmelstoss still refuses to move. Then a commanding officer sees the two:
COMMANDER: Forward! Forward! Get out here!
HIMMELSTOSS: The command was forward. Command was forward! Forward! Forward!
At the command, Himmelstoss leaps from the crater and bravely charges the enemy line as Paul looks on in surprise and, perhaps, with a hint of admiration.
This shows us that Himmelstoss's obsession with status and rank works both ways. While he demands that those of a lower rank respect and obey his orders, he respects those ranked above him, obeys their commands, and seeks desperately to please them. For him, status is currency and rank is how you earn it.
Not that it works out for him at the Front. He's hit soon after taking up the charge.