In early 1962, the Nationalists were tempted to try to exploit the serious economic difficulties in China to retake the Chinese mainland. In his New Year message, President Chiang Kai-shek asserted that the Government of Republic of China was preparing a major offensive and stood ready to assist mainland uprisings against the Communist. Although, his declaration implied that the United States could be expected to support such Nationalist military operations on the mainland. However, the implication in his New Year message was just his subjective wishful thinking. The main purpose of the thesis is to apply Graham Allison’s decision-making models, namely Rational Actor Model (RAM), Organizational Behavior Model (OBM), and Governmental Politics Model (GPM), to explore the Kennedy and Johnson administrations’ position and policy toward Taipei’s policy of “Retaking the Chinese Mainland.” To begin with the RAM, both John F. Kennedy (JFK) and Lyndon B. Johnson (LBJ) did not want the Nationalist to return to the mainland. JFK finally decided to persuade Chiang to postpone his policy of “Return to Mainland,” whereas LBJ directly turned down Chiang’s request of American support for fear that U.S. would be dragged into war with Mainland China. JFK assigned the Assistant Secretary of State for Far Eastern Affairs, W. Averell Harriman, to show U.S. positions to GRC. First, the U.S. continued to assume that all discussions of “return to the mainland” were governed by the understanding in the exchange of notes between U.S. Secretary of States and Chinese Minister of Foreign Affairs on December 10, 1954. Second, the U.S. believed that most careful studies were necessary of both intelligence and operational planning for proposed new venture. “You may draw, if you wish, on the Cuban Bay of Pigs misadventure as a proof of the dangers of bad intelligence, and a decision based more on hope than reality. You should emphasize our insistence on continued detailed intelligence and exchange of views,” Washington told Taipei. Finally, “Our earlier approval of 20-man drops was heavily connected with the fact we were no involved 200-man teams with U.S. air support are a wholly different matter, and while we too will await results of further study, you should indicate that support for such drops would be a major shift in policy for us and would have to be supported by compelling evidence,” the U.S. government added.As for the OBM, there are five fundamental gaps between what JFK actually approved and what he thought he was approving arose from at least three sources. First, they arose in part because the President just became the master of the White House. He did not fully know the strengths and weaknesses of his advisers respectively. He didn’t feel he could trust his own instincts against the judgments of experts. Second, these gaps arose in part because the pressures of time and secrecy permitted too little consideration of the plan and its merits by anyone other than its authors and advocates. Only the CIA and the Joint Chiefs of Staff (JCS) had an opportunity to study and ponder the details of the plan. Finally, these gaps arose in part because the new administration had not yet fully organized itself for crisis planning, enabling the pre-committed authors and advocates of the project in the CIA and JCS to exercise a dominant influence.As for the GPM, if backing Chiang in his last dramatic gamble was against U.S. interests, Ambassador to the Republic of China Everett F. Drumright and Deputy Director of the CIA Ray S. Cline felt that the United States would shortly get a major approach from the GRC. Instead of waiting for it, there might be some advantages in jumping first by telling them how the U.S. government looked at the situation. Besides, American policy grew for the President’s belief that the People’s Republic of China was an expansionist and threatening power. The restraint demonstrated by the Chinese Communists in circumstances such as the Taiwan Straits did not alter Kennedy’s view that the United States confronted an aggressive Chinese expansionism. Kennedy’s fear of domestic political reprisals also worked to prevent him from introducing new elements into China policy. While the “Delay Policy” was the one that helped to contribute to the resolution of the 1962-1963 Taiwan Strait Crisis, President Kennedy decided to receive Secretary of State Dean Rusk’s suggestion and thought about the painful task of dissuading Chiang. Accordingly, although the U.S. supported the Nationalists to impede Communist China’s expansion, JFK accepted Dean Rusk and W. Averell Harriman’s suggestion, and LBJ decided to ignore Chiang’s ideas by lending no support to the “Retaking the Chinese Mainland” policy to protect the national interest of the United States.