In September 1944, the Soviet Red Army and its allies crossed into Hungary and by December 1944, had encircled the capital, Budapest, starting a siege of the city. In February 1945, Budapest was taken. The last German troops were expelled from Hungary in early April 1945; Soviet operations ended on April 4, 1945, although a number of small German-Hungarian units continued to resist until the end of the war. In post-war Hungary, April 4 was celebrated as Liberation Day until 1989.
(Taken from Soviet Counter-Attack and Defeat of Germany – Wars of the 20th Century – World War II in Europe)
The Balkans and Eastern and Central Europe With its advance into western Ukraine in April 1944, the Red Army, specifically the 2nd and 3rd Ukrainian Fronts, including the 1st and 4th Ukrainian Fronts, was poised to advance into Eastern Europe and the Balkans to knock out Germany’s Axis allies from the war. In May 1944, a Red Army offensive into Romania was stopped by a German-Romanian combined force, but a subsequent operation in August broke through, and the Soviets captured Targu Frumus and Iasi (Jassy) on August 21 and Chisinau on August 24. The Axis defeat was thorough: German 6th Army, which had been reconstituted after its destruction in Stalingrad, was again encircled and destroyed, German 8th Army, severely mauled, withdrew to Hungary, and the Romanian Army, severely lacking modern weapons, suffered heavy casualties. On August 23, Michael I, King of Romania, deposed the pro-Nazi government of Prime Minister Ion Antonescu and announced his acceptance of the armistice offered by Britain, the United States, and the Soviet Union. Romania then switched sides to the Allies and declared war on Germany. The Romanian government thereafter joined the war against Germany, and allowed Soviet forces to pass through its territory to continue into Bulgaria in the south.
The rapid collapse of Axis forces in Romania led to political turmoil in Bulgaria. On August 26, 1944, the Bulgarian government declared its neutrality in the war. Bulgarians were ethnic Slavs like the Russians, and Bulgaria did not send troops to attack the Soviet Union and in fact continued to maintain diplomatic ties with Moscow during the war. However, its government was pro-German and the country was an Axis partner. On September 2, a new Bulgarian government was formed comprising the political opposition, which did not stop the Soviet Union from declaring war on Bulgaria three days later. On September 8, Soviet forces entered Bulgaria, meeting no resistance as the Bulgarian government stood down its army. The next day, Sofia, the Bulgarian capital, was captured, and the Soviets lent their support behind the new Bulgarian government comprising communist-led resistance fighters of the Fatherland Front. Bulgaria then declared war on Germany, sending its forces in support of the Red Army’s continued advance to the west.
The Red Army now set its sights on Serbia, the main administrative region of pre-World War II Yugoslavia. Yugoslavia itself had been dismembered by the occupying Axis powers. For Germany, the loss of Serbia would cut off its forces’ main escape route from Greece. As a result, the German High Command allocated more troops to Serbia and also ordered the evacuation of German forces from other Balkan regions.
Occupied Europe’s most effective resistance struggle was located in Yugoslavia. By 1944, the communist Yugoslav Partisan movement, led by Josip Broz Tito, controlled the mountain regions of Bosnia, Montenegro, and western Serbia. In late September 1944, the Soviet 2nd and 3rd Ukrainian Fronts, thrusting from Bulgaria and Romania, together with the Bulgarian Army attacking from western Bulgaria, launched their offensive into Serbia. The attack was aided by Yugoslav partisans that launched coordinated offensives against the Axis as well as conducting sabotage actions on German communications and logistical lines – the combined forces captured Serbia, most importantly the capital Belgrade, which fell on October 20, 1944. German forces in the Balkans escaped via the more difficult routes through Bosnia and Croatia in October 1944. For the remainder of the war, Yugoslav partisans liberated the rest of Yugoslavia; the culmination of their long offensive was their defeat of the pro-Nazi Ustase-led fascist government in Croatia in April-May 1945, and then their advance to neighboring Slovenia.
The succession of Red Army victories in Eastern Europe brought great alarm to the pro-Nazi government in Hungary, which was Germany’s last European Axis partner. Then when in late September 1944, the Soviets crossed the borders from Romania and Serbia into Hungary, Miklos Horthy, the Hungarian regent and head of state, announced in mid-October that his government had signed an armistice with the Soviet Union. Hitler promptly forced Horthy, under threat, to revoke the armistice, and German troops quickly occupied the country.
The Soviet campaign in Hungary, which lasted six months, proved extremely brutal and difficult both for the Red Army and German-Hungarian forces, with fierce fighting taking place in western Hungary as the numerical weight of the Soviets forced back the Axis. In October 1944, a major tank battle was fought at Debrecen, where the panzers of German Army Group Fretter-Pico (named after General Maximilian Fretter-Pico) beat back three Soviet tank corps of 2nd Ukrainian Front. But in late October, a powerful Soviet offensive thrust all the way to the outskirts of Budapest, the Hungarian capital, by November 7, 1944.
Two Soviet pincer arms then advanced west in a flanking maneuver, encircling the city on December 23, 1944, and starting a 50-day siege. Fierce urban warfare then broke out at Pest, the flat eastern section of the city, and then later across the Danube River at Buda, the western hilly section, where German-Hungarian forces soon retreated. In January 1945, three attempts by German armored units to relieve the trapped garrison failed, and on February 13, 1945, Budapest fell to the Red Army. The Soviets then continued their advance across Hungary. In early March 1945, Hitler launched Operation Spring Awakening, aimed at protecting the Lake Balaton oil fields in southwestern Hungary, which was one of Germany’s last remaining sources of crude oil. Through intelligence gathering, the Soviets became aware of the plan, and foiled the offensive, and then counter-attacked, forcing the remaining German forces in Hungary to withdraw across the Austrian border.
The Germans then hastened to construct defense lines in Austria, which officially was an integral part of Germany since the Anschluss of 1938. In early April 1945, Soviet 3rd Ukrainian Front crossed the border from Hungary into Austria, meeting only light opposition in its advance toward Vienna. Only undermanned German forces defended the Austrian capital, which fell on April 13, 1945. Although some fierce fighting occurred, Vienna was spared the widespread destruction suffered by Budapest through the efforts of the anti-Nazi Austrian resistance movement, which assisted the Red Army’s entry into the city. A provisional government for Austria was set up comprising a coalition of conservatives, democrats, socialists, and communists, which gained the approval of Stalin, who earlier had planned to install a pro-Soviet government regime from exiled Austrian communists. The Red Army continued advancing across other parts of Austria, with the Germans still holding large sections of regions in the west and south. By early May 1945, French, British, and American troops had crossed into Austria from the west, which together with the Soviets, would lead to the four-power Allied occupation (as in post-war Germany) of Austria after the war.