Word of the exchange between the American advance to Berlin and the Soviet forces reaches Moscow and Washington D.C. , and it was confirmed that the US had crossed the agreed occupation boundaries . Stalin believes that both he and the US had voided the Yalta agreements and now , technically , the United States and Soviet Union are '' de facto '' enemies . Combined with his paranoia that the West wants to take the Soviet Union 's chance of revenge on Germany from him and refuses to allow it , with the invalidated postwar divide already causing hostilities , he decides to conquer and occupy Germany and then all of Europe while the Soviet Union still has the chance , thus starting another world war
Yalta agreements
Yalta Conference
Red Inferno: 1945