This image shows the “big three” leaders meeting at yalta in february 1945, where they continued making plans that would eventually lead to the united nations. this image best demonstrates which idea about us involvement in planning the united nations? a) harry s. truman was the president when the united nations formed. b) the cold war broke ties between the united states and soviet union. c) the united states held on to an isolationist position in foreign policy. d) united states leaders were crucial to the planning of the united nations.