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 Bf 109-Es so they could receive the new Bf 109-F variant. Transition training was completed at Airfield Stolp-Reitz in Pomerania. Following intensive training, the "Geschwader" was moved to airfields in Eastern Prussia. On 22 June at 03:05, 120 aircraft of the "Geschwader" crossed into Soviet airspace in support of Operation Barbarossa, the invasion of the Soviet Union. Philipp, like many other German fighter pilots, enjoyed superiority over his Soviet adversaries in the early phase of Barbarossa, both in terms of the training he had received and the aircraft that he flew. He quickly accumulated further victories and on account of his 31st to 33rd victories achieved on 4 July was mentioned in the "Wehrmachtbericht" radio report, the first of five such mentions, on 7 July.