In the early 1949, Mao Tse-tung took notice of the complexity of the United States factor in the Taiwan issue. While the People's Literation Army (PLA) was seriously preparing to establish an air force, navy and parachute troops in order to serize Taiwan, the Korean War broke out in June of 1950. Harry Truman, the President of the United States, ordered the Seventh Fleet to defend Taiwan against any PLA invasion. Undoubtedly, this circumstance obstructed Mao's plan to liberate Taiwan by force. The plan to invade Taiwan was further postponed at the time when Mao decided to take military intervention in the Korean War. After the conclusion of the Korean War, Mao obviously did not intend to engage in a massive military conflict with U.S. once again. Hence, during the first Taiwan Straits crisis, Mao tried his best to prevent anything that would cause U.S. military involvement. During the second Taiwan Straits crisis, Mao was more cautious than ever and was commanding the campaign personally. In that period of time, the U.S. factor always played a critical role in Mao's decision-making. Because of the dispute between U.S. and Chiang Kai-shek over the withdrawal of armed forces from Quemoy and Matsu, Mao was inspired to make use of the conflict between them. Mao made one important decision to give up the original plan in order to force the Nationalist army to withdraw from Quemoy and Matsu. Then he proposed the new idea to let CKS keep Quemoy and Matsu. This served two purposes at the same time. First, it would assist to extend the disagreement between U.S. and CKS. Second, U.S. would be trapped in the struggle of Nationalist defense of Quemoy and Matsu. Mao said that was “Hanging Policy”. Over that period, Mao and CKS were exchanging messages via secret messenger. The second Taiwan Straits crisis finally came to an end. During these two Taiwan Straits crises, Mao always took extra precautions against U.S. Mao was the sole decision-maker, while Zhou En-lai was just executing Mao's policy.