The Cold War was an important cause in the Korean War. Relations between the two occupying powers were bad and when China became Communist in October 1949, the President of the USA, Harry Truman, was very worried that other countries around China may also become Communist, such as Japan. The American Army was about one twelfth the size of five years earlier and Joseph Stalin had recently lost a Cold War dispute over the Berlin Blockade and subsequent airlift. They mainly argued over fair border lines and the spread of communism therefore starting the war.