Following his tour as an instructor, Willius returned to 3. "Staffel" on 31 March 1943. In 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. At the time of Willius' return to his unit, the "Gruppe" was based at Dno and fighting in the vicinity of Demyansk, during and following the Battle of Demyansk in support of the 16th Army and 18th Army.