The administration of J.F.K. determined that the mission and size of the U.S. advisory project must increase if the U.S.-backed government in Saigon was to survive and win the war. While some of Kennedy's cabinet advisors proposed a negotiated settlement for Vietnam similar to one that recognized Laos as a neutral nation, this was not to be. The administration had just suffered diplomatic setbacks and embarrassments in Berlin and Cuba. So that it did not repeat this, the covert military option was used, but unsuccessfully. The war continued to escalate, requiring more U.S. advisors and military and foreign aid. Unfortunately for the U.S., the covert operations to assist the South against North Vietnam escalated in the harassment and landing of covert forces until the U.S. Navy became embroiled in the Gulf of Tonkin incident that sealed the U.S. path to open military involvement in the conflict (ibid.).
Diplomatic options in Vietnam definitively died as the South Vietnamese government took action against demonstrating Buddhist monks and students in August of 1963. In a fascinating series of memos and audio recordings available to the public online through the auspices of the National Security Archive at George Washington University. At this time, Kennedy had decided upon a coup against Ngo Dinh Diem if he did not remove his brother Ngo Dinh Nhu who the administration was convinced would lose the war due to the oppressive policies. J.F.K. recognized that the Congress might be angry at him for supporting Vietnamese generals in a coup against Diem. However, Kennedy remarked that it will "be madder if Vietnam goes down the drain ("Kennedy considered supporting," 2009)." The administration then considered proposals to evacuate American troops from South Vietnam as explicitly linked to the success of a military coup. The administration tapes reveal that the plans for the American withdrawal were created in fabric of the NSC deliberations about the coup. The coup rumors and threats were waved as a feature of diplomatic maneuvers to induce President Diem to oust his brother Nhu from the government (ibid.). The failure of the administrations policies in the wake of the Diem coup ensured the escalation of the U.S. intervention. As with George W. Bush later, this cavalier attitude toward assassination would raise long lasting constitutional questions that impacted upon civilian rights.
As we have seen, the flexible response doctrine had advantages and disadvantages on the military and diplomatic fronts. After the Cuban Missile Crisis, the U.S. ended overt military efforts against Cuba, but kept up a diplomatic and covert offensive that continues to isolate the island to this day. While the efforts failed to overthrow Castro, they did succeed in maintaining pressure on and containing him for the time.
Unfortunately, this was not to work in Vietnam, where it became overtly involved militarily in the conflict. In the opinion of this author, what we therefore see in Vietnam was the demise of the doctrine of flexible response. In a seemingly inevitable spiral, diplomacy, economic and covert means became a quagmire that demanded full military intervention or withdrawal. Diplomacy, economic pressure, military assistance and covert intervention was not help, even in containing the North Vietnamese forces north of the border. In this, case, the target was not in the American backyard, but half a world away in Southeast Asia. Like in Korea previously, the U.S. became embroiled in an Asian shooting war. Tragically, in the case of Vietnam, it had to overthrow the regime that the U.S. had supported since the Eisenhower administration. The failure of this coup almost certainly sealed the future escalation of the war for the U.S. And cut off diplomatic and other options from the American "tool kit" in the Vietnam situation.
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