Army Group Ostmark (Heeresgruppe Ostmark) was a German army group formed very late in World War II. Army Group Ostmark was formed on 2 April 1945 from the remnants of Army Group South (Heeresgruppe Süd). Army Group Ostmark was operational in Austria and Czechoslovakia. Army Group Ostmark was one of the last major German military formations to surrender to the Allies. The only commander of this army group, Dr. Lothar Rendulic, surrendered it in Saint Martin, Upper Austria, on May 7, 1945.