On 22 June 1941 the Germany army launched a massive invasion of the Soviet Union, in flagrant defiance of the (formally still in most respects secret) non-aggression pact concluded between the German and Soviet dictators slightly less than two years earlier. In Moscow, Leo Stern volunteered for service with the Soviet Red Army on 7 July 1941. He served as a Soviet army officer between 1942 and 1945, concluding the war as a bemedaled "Lieutenant Colonel", and then serving for a further five years as an officer in the Soviet army of occupation in Vienna. Records indicate that during the initial part of his time with the Red Army he was assigned to a number of "special projects", at least some of which seem to have involved desk-bound work. During the early part of 1942 he composed a series of "teaching aids" on Austrian History and the History of the Austrian Labour Movement for the "International Lenin School", relocated, between 1941 and 1943, from Moscow to Kushnarenkovo in Bashkortostan. Of possibly greater immediate importance in terms of Soviet strategic objectives was the work Stern undertook with Johann Koplenig (1891-1968) to create a "Committee of Austrian Liberation Movements".