In early 1941, he underwent training as a Stuka pilot.[10] He was posted to 1 Staffel Sturzkampfgeschwader 2 (StG 2), which was moved to occupied Poland in preparation for Operation Barbarossa, the invasion of the Soviet Union, in June 1941.[8] On 21 September 1941, Rudel took part in an attack on the Soviet battleship Marat of the Baltic Fleet.[8] Marat' was sunk at her moorings on 23 September 1941 after being hit by one 1,000-kilogram (2,200 lb) bomb near the forward superstructure.