The Eastern Front had been relatively stable since the end of Operation Bagration in late 1944. The Germans had lost Budapest and most of Hungary. Romania and Hungary were forced to surrender and declare war on Germany. The Polish plain was open to the Soviet Red Army.
The Soviet commanders, after waiting for the Germans to reduce the Polish Home Army, took Warsaw in January 1945. Over three days, on a broad front incorporating four army groups (fronts,) the Red Army began an offensive across the Oder River and from Warsaw. After four days the Red Army broke out and started moving twenty to twenty-five miles a day, conquering the Baltics, Danzig, East Prussia, Poznan, and drawing up on a line thirty-six miles outside of Berlin.
A counterattack by the newly created Army Group Vistula failed by February 24, and the Russians drove on Pomerania and cleared the right bank of the Oder River. In the south, three attempts to relieve the encircled Budapest failed and the city fell on February 13. Again the Germans counterattacked, Hitler insisting on the impossible task of regaining the Danube River. By March 16 the attack had failed and the Red Army counterattacked the same day. On March 30 they entered Austria and captured Vienna on April 13.
Only a twelfth or less of the gasoline needed by the Wehrmacht was available. Fighter and tank production was down, and the quality was much less than in 1944. The war was clearly over, but the Germans would hold out for almost a month. The fighting was would be fierce; national pride and the desire to gain time for refugees to get to the west led German units to fight bitterly.
By April 1, 1945, the Russians were outside Berlin. They built up for two weeks, knowing that Berlin would be heavily contested. The Western Allies planned to drop paratroops to take Berlin, but decided against it. Eisenhower saw no need to suffer casualties taking a city that would be in the Soviet sphere of influence once the war was over.
Adolf Hitler, who never thought Berliners supported him the way he deserved, decided to remain in the city. Some think he remained to punish the city for lack of support in the early days of Nazism; more likely there was nowhere to go. The Battle of Berlin would be the deciding conflict between Nazism and Communism.
The offensive began with thousands of artillery and rockets called “Stalin Organs” for their hideous shrieking noise opening a huge sustained barrage for days. On April 16, the First and Second Belorussian Fronts and the First Ukrainian Front, which boxed in Berlin from the North, West, and South, attacked. By April 24 the three army groups had completed the encirclement of the city.