The order for the invasion had been put forward in "Führer Directive No. 25", which Adolf Hitler issued on 27 March 1941, following the pro-British Yugoslav coup d'état in Belgrade. He claimed his first aerial victory on 7 April 1941, when he shot down a Yugoslav Royal Air Force Hawker Hurricane fighter. JG 54 continued flying ground support missions during the Balkans Campaign. Following the surrender of the Royal Yugoslav Army on 17 April 1941, while stationed at an airfield at Zemun near Belgrade, the "Geschwader" received orders on 3 May 1941 to turn over all Messerschmitt Bf 109-Es to "Jagdgeschwader" 77 (JG 77—77th Fighter Wing) so they could receive the new Bf 109-F variant. Transition training was completed at Airfield Stolp-Reitz in Pomerania. Following the Balkans Campaign, Beißwenger was awarded the Iron Cross 2nd Class () on 6 May 1941.