How did Stalin work with Roosevelt and Churchill to achieve his goals?

Many of the major decisions that Soviet Premier Josef Stalin came to with U.S. President Franklin Roosevelt and British Prime Minister Winston Churchill occurred at the Yalta Conference.

When the three country leaders met at Yalta, the countries already felt certain that they would defeat the Nazi influence in Europe. However, Churchill and Roosevelt recognized that getting the Soviet Union involved in the fight in the Pacific could be advantageous in helping them attain victory there as well.

Though Stalin agreed to send Russian troops to assist in the Pacific to fight against Japan, he had the upper hand in negotiations, as the Soviet Union didn't necessarily need to fight in the Pacific.

Upon agreeing to join with U.S. and British forces at the Yalta Conference, Stalin negotiated his country's participation and influence for the time when Japan would surrender. The Soviet Union was able to gain influence in the southern part of Sakhalin and the Kurile Islands. Perhaps more importantly, the Soviet Union would gain a share in operating the Manchurian railroads.

Stalin also negotiated with Churchill and Roosevelt how the countries would relate with European countries after the countries were liberated from the Nazi regime. Stalin negotiated the inclusion of communists in post-war Poland government posts. During negotiations, Stalin also got Churchill and Roosevelt to agree that countries bordering the Soviet Union should be friendly to the Soviet regime.