In the 1950s, the Republic of China (ROC) on the island of Taiwan was a Cold War ally of the United States. Led by President Chiang Kai-shek and his ruling Kuomintang Party, the ROC received military, financial, and humanitarian assistance from the U.S., and enjoyed support in the White House, from the Departments of State and Defense, the Central Intelligence Agency (CIA), and the Democratic and Republican Parties. President Chiang even employed public relations firms and political pressure groups to help generate public support and to sway American policymakers to favor his cause. By the end of the 1970s, however, the ROC had lost its seat in the United Nations and no longer maintained formal diplomatic relations with the United States. Why would the United States abandon a long-standing World War II ally, recipient of American aid, and fellow anti-communist? The 1960s proved to be a pivotal decade in the diplomatic and military relationship between the United States and the ROC. Presidents John F. Kennedy and Lyndon B. Johnson, both Democrats, publicly promised support for Chiang and the Chinese Nationalists on Taiwan. Chiang hoped to secure continued military aid and diplomatic support by relying upon allies in the State Department, the Central Intelligence Agency, and in the U.S. Congress, and even occasionally making threats to take actions detrimental to American policy. Throughout the 1960s, the U.S.-ROC relationship was tested by events in the United Nations, the Taiwan Strait, and Southeast Asia. By the end of the decade, the ROC had lost millions in American aid and the United States had publicly started to consider normalizing relations with the People?s Republic of China. This dissertation will show that U.S.-ROC relations in the 1960s deteriorated due to a combination of factors. The Vietnam War was one of several factors that helped bring an end to formal American relations with the Republic of China. The Vietnam War caused a conflict of interest, whereby American containment of communism in Southeast Asia clashed with ROC plans to maintain its international legitimacy and to restore its rule over all China. Additionally, bureaucratic changes within the State Department, the demise and ineffectiveness of the China Lobby, and the changing make-up of the United Nations resulting from decolonization also contributed to the decline of U.S.-ROC relations.