Why did Stalin agree to a non aggression treaty with Germany?

Stalin agreed to a non-aggression treaty with Germany, known as the Molotov-Ribbentrop Pact, in 1939 primarily to secure the Soviet Union's western borders and buy time to strengthen its military. The treaty allowed the USSR to avoid a two-front war and gain strategic advantages, including territorial expansions in Eastern Europe. Additionally, Stalin sought to counterbalance the rising threat of Nazi Germany while maintaining the USSR's influence in the region. The pact ultimately shocked the world, as it seemed to contradict the ideological opposition between fascism and communism.