With the surprise signing of the Molotov–Ribbentrop Pact on 23 August, the result of secret Nazi-Soviet talks held in Moscow , Germany neutralized the possibility of Soviet opposition to a campaign against Poland and war became imminent. In fact, the Soviets agreed not to aid France or the UK in the event of their going to war with Germany over Poland and, in a secret protocol of the pact, the Germans and the Soviets agreed to divide Eastern Europe, including Poland, into two spheres of influence; the western ⅓ of the country was to go to Germany and the eastern ⅔ to the Soviet Union.
Hitler was incensed by this counterthrust but quickly cancelled his order for the invasion. Then, in a wild gamble that France and Great Britain would not meet their treaty obligations to Poland, and knowing he had nothing to fear from the Soviet army, Hitler ordered his troops to strike east into Poland on September 1, 1939. Two days later, on September 3, France and Great Britain declared war on Germany. World War II had begun. And less than two years after that, Hitler scrapped his pact with Stalin and sent some 3 million Nazi soldiers pouring into the Soviet Union on June 22, 1941.