In The Boy in the Striped Pajamas, how does Lt. Kotler abuse his power?

Lieutenant Kurt Kotler is one of  the soldiers at Auschwitz who has sworn allegiance to the Nazi party. Throughout the book, the author shows us how evil operates through an ordinary person such as Kotler, and how this evil manifests itself in the abuse of power. 

Kotler, a young soldier, treats the Jews as sub-human, calling them names and treating them as slaves. Throughout the book, Kotler uses his position of power as a Lieutenant in abusive ways. Bruno first recognizes Kotler’s insolence when Kotler takes away Bruno’s book Treasure Island and waves it in front of Bruno in an effort to anger him. Bruno justifiably dislikes Kotler, as we begin to see his treatment of others.

Throughout the book, Kotler appears to be a bigger and bigger bully. One day, Bruno observes him coldly shooting a stray dog. He also notices how Kotler bullies Pavel, calling him names and eventually beating him for spilling wine. Shmuel is familiar with Kotler’s abuse, as he is beat until bruised after there is evidence that he has befriended Bruno.

Kotler ultimately faces his downfall when he is questioned about his father’s activities in leaving the country when it was illegal to do so. Bruno is pleased with it, but notices that his mother is unhappy, judging from her arguments with his father.