The Vienna offensive was an offensive launched by the Soviet 2nd and 3rd Ukrainian Fronts in order to capture Vienna, Austria, during World War II. The offensive lasted from 16 March to 15 April 1945. After several days of street-to-street fighting, the Soviet troops captured the city on 13 April 1945.
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Vienna offensive in the context of Allied-occupied Austria
At the end of World War II in Europe, Austria was occupied by the Allies and declared independence from Nazi Germany on 27 April 1945 (confirmed by the Berlin Declaration for Germany on 5 June 1945), as a result of the Vienna offensive. The occupation ended when the Austrian State Treaty came into force on 27 July 1955.
After the Anschluss in 1938, Austria had generally been recognized as part of Nazi Germany. In November 1943, however, the Allies agreed in the Declaration of Moscow that Austria would instead be regarded as the first victim of Nazi aggression—without denying Austria's role in Nazi crimes—and treated as a liberated and independent country after the war.
View the full Wikipedia page for Allied-occupied Austria