Complex sentence: As the Soviet Army pushed the Wehrmacht back on the Eastern Front, it became necessary to reactivate "Prinz Eugen" as a gunnery support vessel; on 1 October 1943, the ship was reassigned to combat duty.
Split into simpler sentences: As the Soviet Army pushed the Wehrmacht back on the Eastern Front, it became necessary to reactivate "Prinz Eugen" as a gunnery support vessel. Therefore, on 1 October 1943, the ship was reassigned to combat duty.