In June 1941 Sandberger was appointed chief of Sonderkommando 1a of Einsatzgruppe A. During the first two weeks of the German invasion of the Soviet Union, which began on June 22, 1941, Sandberger traveled with Franz Walter Stahlecker, the commander of Einsatzgruppe A. Sandberger was involved since March 1941 in the distribution of a business plan for the RSHA and a director of the curriculum organization of the schools ("Lehrplangestaltung der Schulen").