January 12, 1945, saw the beginning of the Soviet Vistula-Oder offensive, led by the celebrated marshals Zhukov and Konev. The operation had been prepared for many months during which the Soviet amassed a force of such magnitude that Hitler refused to believe the incoming reports.
World War 2 was pretty much hopeless for the Germans at this time, but decisions made on either side would have a lasting impact on post-war Europe. Hitler had mostly lost his sense of reality and failed to order the trapped German forces in the Courland pocket home, where they could have helped defending; he even sent troops out to Hungary. Zhukov on the other hand, stopped the offensive at the Oder, just a bit over 40 miles from Berlin – but the Soviet front line had become dangerously extended, and he considered pushing on too dangerous.
They each had their detractors: Guderian fell out with Hitler about the failing defense and Chuikov with Zhukov about the stalled offensive. Plenty of room for alternative history writing: would the Soviets have been stopped before they reached the Oder if Guderian’s advice had been followed? Would they have taken Berlin if Chuikov had had his way?
The offensive was halted on February 2. Two days later, the Yalta conference started and all the decisions that would draw the map for decades to come were made.