Wiese was posted to a front-line unit in June 1941, almost two years after the start of World War II. His unit was the "Geschwaderstab" (headquarters unit) of "Jagdgeschwader" 52 (JG 52—52nd Fighter Wing) where he served as an adjutant. On 22 June, the "Geschwader" crossed into Soviet airspace in support of Operation Barbarossa, the invasion of the Soviet Union, which opened the Eastern Front. He claimed his first aerial victory on 23 September 1941 and was awarded the Iron Cross 2nd Class () on 27 September 1941 and the Front Flying Clasp of the Luftwaffe in Silver () on 11 October 1941.