Soon after assuming the presidency, John F. Kennedy adopted a program to achieve a in South Vietnam even as he harbored doubts about the ability of the regime of Ngo Dinh Diem to defeat the growing communist insurgency. As part of this effort, Kennedy replaced Elbridge Durbrow, the U.S. ambassador in Saigon from early 1957, with Frederick Nolting. Durbrow had spent the better part of three years pressing Diem to adopt political and economic reforms, primarily to broaden his government's base of support. Durbrow's approach included threats to withhold U.S. foreign aid if Diem did not adopt the reforms that the embassy recommended. Consistent with the approach adopted by the Kennedy administration, Nolting abandoned Durbrow's tactics, backing Diem unconditionally regardless of the latter's behavior. Durbrow, an ardent cold warrior, was sent to Saigon to manage the U.S. relationship with the regime of Ngo Dinh Diem in the interest of building South Vietnam into a bulwark against the spread of communism in Southeast Asia. Durbrow fully accepted the premises of containment and the domino theory on which the Eisenhower administration based its foreign policy. He soon learned, however, that Diem's regime was failing to provide the bulwark (or even the anticommunist regime) in which the Eisenhower administration was interested (Kaiser 2000, 58-59). Durbrow and other embassy officials in Saigon saw serious flaws in the Diem regime, and their convictions increased with time. With the Eisenhower White House exerting little control over affairs in Saigon at a time when Vietnam was a less important issue than it would become a few years later, Durbrow and the embassy pressured Diem to reform. Ultimately, they needed Washington's support to achieve their goals, the timing was such that the Eisenhower administration did not have to make critical decisions regarding the U.S. commitment to Diem and was able to hand off Vietnam to the Kennedy administration. The institutional record compiled by the embassy raised doubts among key officials of the incoming Kennedy administration, including the president himself, regarding the extent to which U.S. aid was achieving the goal of a stable, anticommunist government in South Vietnam. Nonetheless, for reasons of domestic and international politics, officials in the Kennedy White House and in the Pentagon did not act on the basis of Durbrow's views either. Rather, they pushed forward, adhering to the strategic policy of the Eisenhower (and Truman) administration, but with new vigor added at the tactical level, as Nolting (1966, 2) recalled, in order to buy time for Diem. The appointment of Nolting was one element of the new approach. The administration sent Nolting to Vietnam under the assumption that gaining Diem's confidence was the key to the breakthrough it sought. Given a narrower and more explicit brief than Durbrow, Nolting discarded the latter's carrot-and-stick approach, opting for carrots alone. He believed that a winning spirit among U.S. officials in Washington and Saigon was the best way to help Diem battle the growing communist insurgency. Backing Diem unconditionally and providing sufficient military and security personnel, Nolting surmised, would enable the Saigon regime to gain broad political support and increase its effectiveness. In the process, Washington would also increase its ability to reform Diem, in his view. In carrying out his instructions, however, Nolting conceded much of the leverage that the Kennedy administration hoped to assert over Diem. This study shows how successive presidential administrations redefined ambassadorial roles and how two ambassadors responded, given their instructions. It pays close attention to actions of Durbrow and Nolting at a pivotal moment when Washington opted not to exercise some of the leverage it might have wielded over Diem. …