After the German attack on the Soviet Union in 1941, Birkner and his "Einsatzkommando" were deployed in the newly-formed Bialystok District in the Army Group Centre Rear Area. Birkner arrived in Białystok from the General Government on 30 June 1941, sent in by the SS Police commander Eberhard Schöngarth on orders from the Reich Security Main Office. As veteran of "Einsatzgruppe" IV from the 1939 invasion of Poland, Birkner was a specialist in rear security operations.