during the Soviet Vienna Offensive just before the total collapse of the Third Reich. The invading Allied powers, in particular the Americans, planned for the supposed "Alpine Fortress Operation" of national redoubt that was largely to have taken place on Austrian soil in the mountains of the eastern Alps. However it never materialized because of the rapid collapse of the Reich.
Karl Renner and Adolf Schärf (Socialist Party of Austria [Social Democrats and Revolutionary Socialists]), Leopold Kunschak (Austria's People's Party [former Christian Social People's Party]) and Johann Koplenig (Communist Party of Austria) declared Austria's secession from the Third Reich by the Declaration of Independence on 27 April 1945 and set up a provisional government in Vienna under state Chancellor Renner the same day, with the approval of the victorious Red Army and backed by Joseph Stalin. (The date is officially named the birthday of the second republic.) At the end of April, most of Western and Southern Austria still was under Nazi rule. On 1 May 1945, the federal constitution of 1929, which had been terminated by dictator Dollfuss on 1 May 1934, was declared valid again.
Total military deaths from 1939 to 1945 are estimated at 260,000. Jewish Holocaust victims totaled 65,000. About 140,000 Jewish Austrians had fled the country in 1938–39. Thousands of Austrians had taken part in serious Nazi crimes (hundreds of thousands died in Mauthausen-Gusen concentration camp only), a fact officially recognised by Chancellor Franz Vranitzky in 1992.
Much like Germany, Austria was divided into British, French, Soviet and American zones and governed by the Allied Commission for Austria. As forecast in the Moscow Declaration in 1943, there was a subtle difference in the treatment of Austria by the Allies. The Austrian Government, consisting of Social Democrats, Conservatives and Communists (until 1947) and residing in Vienna, which was surrounded by the Soviet zone,
