This tiny excerpt from a longer article in the distinguished periodical Foreign Affairs explains the China connection to the US involvement in Vietnam.
http://www.foreignaffairs.org/19950501fareviewessay5044/george-c-herring/the-wrong-kind-of-loyalty-mcnamara-s-apology-for-vietnam.htmlMcNamara recalls a dramatic encounter in which Jackie Kennedy literally beat his chest and demanded that he "do something to stop the slaughter."
The secretary of defense was a key figure in decisions to escalate the war between 1961 and 1965, and he readily concedes that the assumptions upon which he and his colleagues acted were badly flawed. They approached Vietnam, he recalls, with "sparse knowledge, scant experience and simplistic assumptions." Victims of their own "innocence and confidence," they foolishly viewed communism as monolithic, knew nothing about Indochina, and were "simple?minded" regarding the historical relationship between China and Vietnam.
"In the lands of the blind, one?eyed men are king," said President Eisenhower in 1954, explaining his decision, against the recommendations of many of his expert advisers, to aid South Vietnam's Ngo Dinh Diem. Kennedy fell victim to the same delusion, as did Johnson.
No political figure, especially a Democrat, was prepared to risk the fate that had befallen Harry Truman and Dean Acheson for the loss of China. Despite his doubts, Kennedy refused even to consider withdrawal from Vietnam until he had been safely reelected. Johnson repeatedly insisted that he was not going to be the president to see Vietnam go the way of China.
http://www.cnn.com/SPECIALS/cold.war/episodes/11/interviews/mcnamara/Robert McNamara was interviewed for this episode of COLD WAR in June 1996.
On why the United States became involved in Vietnam: [The domino theory] was the primary factor motivating the actions of both the Kennedy and the Johnson administrations, without any qualification. It was put forward by President Eisenhower in 1954, very succinctly: If the West loses control of Vietnam, the security of the West will be in danger. "The dominoes will fall," in Eisenhower's words.
I [McNamara] was determined -- to avoid the risks that would follow from applying unlimited military force [on North Vietnam]. In addition to a terrible loss of life that would have resulted from that, there was ... a risk of overt confrontation between the U.S. and China and the Soviet Union, overt military confrontation, including the possible use of nuclear weapons.
On the war in general:But today, General Westmoreland, who was the commander in Vietnam at the time, says that while at the time he felt he was constrained, he now understands that that was an effort by the president to prevent the U.S. coming into open military conflict with China and the Soviet Union.
Conclusion:We'll have lost 160 million people, killed by conflict. Is that what we want in the 21st century? I don't think so. If we want to avoid it, we have to learn from our mistakes in this century. Vietnam was one of those.