The Vienna Offensive occurred from 2 to 13 April 1945 when the Soviet 3rd Ukrainian Front under Marshal Fyodor Tolbukhin and the Bulgarian 1st Army under Vladimir Stoychev launched an offensive against the city of Vienna, the most important city in the German province of Ostmark (as well as the prewar and postwar capital of an independent Austria). Over 745,000 Soviet and Bulgarian troops took part in the heavy fighting, and Vienna fell on 13 April 1945.
Sepp Dietrich's 6th SS Panzer Army withdrew from Hungary after the failure of Operation Spring Awakening, and the Soviets rapidly advanced through Hungary. On 30 March 1945, the Soviets crossed the Hron and Nitra rivers after taking Sopron and Nagykanisa, and most of the German defenders evacuated the city as it was declared to be an "open city". The II SS Panzer Corps and some garrison units were the only forces available to defend the city, and the Soviets advanced into Vienna with ease in some parts and heavy resistance in other parts. On 13 April 1945, Wilhelm Bittrich's panzer corps withdrew from Vienna to avoid encirclement, and the city fell to the Soviets. The offensive drove the Germans back to a new defensive line in the northwest, where they would end the war on 8 May 1945.