苏德互不侵犯条约
Four days later, the Soviet Union and Germany signed the Molotov–Ribbentrop Pact, an agreement of mutual non-aggression between the parties. The Molotov–Ribbentrop Pact contained secret protocols dividing the states of Northern and Eastern Europe into German and Soviet "spheres of influence." At the time, Stalin considered the trade agreement to be more important than the non-aggression pact. One week after the Molotov–Ribbentrop Pact, the partition of Poland commenced with the German invasion of western Poland.