The Vistula-Oder Offensive was a successful Red Army operation on the Eastern Front in the European Theatre of World War II; it took place between 12 January, 1945 and 2 February, 1945. The offensive took Soviet forces from their start lines on the Vistula river in Poland to the Oder river deep in Germany, about seventy kilometers from the capital Berlin.
In the wake of the successful Operation Bagration the 1st Belorussian Front managed to secure two bridgeheads west of the Vistula river between 27 July and 4 August 1944. The Soviets remained inactive during the failed Warsaw uprising that started on August 1, 1944, though their frontline was not far from the insurgents. The 1st Ukrainian Front captured an additional large bridgehead at Sandomierz (known as the Baranow bridgehead in German accounts) during the Lvov-Sandomierz Offensive.
Preceding the offensive, the Soviets had built up large amounts of materiel and manpower in the three bridgeheads. The Soviets greatly outnumbered the opposing German army in infantry, artillery, and armour. All this was known to German intelligence and General Reinhard Gehlen, head of Fremde Heere Ost passed his assessment to Heinz Guderian. Guderian presented the intelligence results to Adolf Hitler, who refused to believe them, dismissing the apparent Soviet strength as "the greatest imposture since Genghis Khan". Guderian had proposed to evacuate the divisions of Army Group North trapped in the Courland Pocket to the Reich via the Baltic Sea to get the necessary manpower for the defence, but Hitler forbade it. In addition, Hitler commanded that one major operational reserve, the troops of Sepp Dietrich's Sixth SS Panzer Army, were moved to Hungary to support Operation Frühlingserwachen.
When the soldiers of the Red Army of the Soviet Union arrived at Auschwitz on January 27, 1945, they were expecting to find more gas chambers; the gassing of the Jews had been common knowledge since June 1942 when the news was first broadcast over the radio by the BBC. What they found was the ruins of four large gas chambers where around one million Jews had been gassed. The Nazis had attempted to destroy the evidence of the genocide of the Jews, but had left behind at least 1,200 survivors at the Auschwitz main camp and 5,800 survivors at Birkenau, including 611 children, who were able to tell the liberators about the monstrous crimes that had been perpetrated at Auschwitz-Birkenau.