They regularly executed POWs and the ones who weren't were sent to concentration camps to be used as slave labor.

This is glossed over so frequently. The USSR casualties include three million POWs who were taken prisoner by the Germans and then systematically starved and worked to death. There's no other POW population on no side of WW2 that comes anywhere close to suffering casualties like this. When you were in the Red Army and taken captive by the Wehrmacht, it basically meant you were being put in a death camp.