Answer:
The U.S and the U.S.S.R
Step-by-step explanation:
The breakdown between the United States and the Union Of Soviet Socialist Republics was after WW2, with the Eastern Block being established and the first conflict of the war being fought in Korea. The U.S.S.R backed the communist north, while America and NATO stepped in on behalf of the South. With both countries having the atomic bomb and the Truman Doctrine being established, all of these marked the start of the Cold War.