Answer :
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In this case, before invading Poland, Hitler reached a secret agreement with the **Soviet Union**. This agreement, known as the Molotov-Ribbentrop Pact, was signed on August 23, 1939. It was a non-aggression pact between Nazi Germany and the Soviet Union, which included a secret protocol dividing Eastern Europe into spheres of influence for the two countries. This pact allowed Hitler to invade Poland without the fear of Soviet intervention.
So, the correct answer to the question is the **Soviet Union**. If you have any more questions or need further clarification, feel free to ask!
