January 1943, the Luftwaffe planned to move JG 26 to the Eastern Front. The idea was to exchange JG 26 with Jagdgeschwader 54 (JG 54—54th Fighter Wing) which supported Army Group North. In order to keep up operations, the exchange was planned by rotating each Gruppe by Gruppe and every Staffel by Staffel. In this context, Mietusch's 7. Staffel was attached to I. Gruppe of JG 54 which was commanded by Hauptmann Hans Philipp and was based outside of Leningrad. On 17 February, 7. Staffel left Courtrai, heading east by train. Following a stop at Heiligenbeil, the unit was based at the airbase at Krasnogvardeysk, present day Gatschina, which is located approximately southwest of Leningrad. At Heiligenbeil, 7. Staffel received 13 new Fw 190 A-4 and A-5 fighters. The combat area of I. Gruppe of JG 54 was predominantly over the front of 18th Army, on the left flank of Army Group North, and on the Volkhov River. In early May, 7. Staffel moved to an airfield at Siverskaya. Mietusch claimed his first aerial victories on the Eastern Front on 21 May. The Staffel was scrambled at 05:25 and ordered to intercept a flight of Petlyakov Pe-2 bombers, escorted by Lavochkin-Gorbunov-Gudkov LaGG-3 fighters, on a mission to bomb a railway bridge at Narva. 7. Staffel claimed five aerial victories on this mission, two Pe-2 bombers and three LaGG-3 fighters shot down, including a Pe-2 and two LaGG-3s by Mietusch. On 13 June on the Western Front, the Gruppenkommandeur (group commander) of III. Gruppe, Hauptmann Kurt Ruppert was killed in action. Command of the Gruppe was temporarily given to Hauptmann Rolf Hermichen. On 29 June, Geschwaderkommodore Priller informed Mietusch that he had been chosen as new commander of III. Gruppe. Mietusch passed command of 7. Staffel to Hauptmann Günther Kelch and returned to Germany. Group commander and death On 5 July, Mietusch arrived at Cuxhaven-Nordholz Airfield where III. Gruppe was based and took over command from Hermichen. In July, the Gruppe received the Bf 109 G-4 and G-6 variants and the pilots began familiarizing themselves with this aircraft type while flying in Defense of the Reich. On the night of 24/25 July, the RAF and USAAF launched Operation Gomorrah, the attack on Hamburg during the last week of July 1943. The RAF initiated the attack at night which created a firestorm in the city. The following day, the USAAF attacked Hamburg