The Comintern (USSR and Its Allies) and the Allies Winning World War 2, and the Cold War Beginning. The Korean War was part of American efforts to stop the Spread of Communism, and the Division of Germany was supposed to be a way to neither give Germany to the Communists or to Give Germany to Democrats. NATO was formed to protect Democratic nations against Authoritarian Regimes like the USSR and the PRC. So Overall, It was a Reaction to the beginning of the Cold War. I could be over-complicating it but I'm not sure. Hope it Helped.