Complex sentence: Prinz next took part in Operation Barbarossa the invasion of the Soviet Union by now promoted to Hauptsturmführer (Captain), he was awarded the Eastern Front Medal for service during the first Russian winter of the war.
Split into simpler sentences: Prinz next took part in Operation Barbarossa, the invasion of the Soviet Union. By now promoted to Hauptsturmführer (Captain), he was awarded the Eastern Front Medal for service during the first Russian winter of the war.