the Khmer Rouge in Cambodia.<ref>The Economist, February 26, 1983; Washington Post, April 23, 1985.</ref>
The [[Kennedy]] administration, which had repeatedly intervened to halt right-wing coups, acquiesced in November 1963 to the overthrow of the weak South Vietnam leader Diem by a coalition of generals. President Nixon would later characterize this decision as a catastrophic betrayal of an ally that contributed to the ultimate disintegration of South Vietnam. The casus beli for full military combat intervention of by the United States was an alleged attack on two US Navy ships by North Vietnam in 1964; it became known as the "Gulf of Tonkin Incident". President Johnson had the US respond with a massive bombing campaign called "Operation Rolling Thunder". Although a swift victory over North Vietnam would have taken a matter of months, the risk of Chinese intervention was considered too great to accept. Thus, Vietnam was fought to avoid "another Korea".
President Johnson, a tormented but ultimately sincere man, could not bear the burden of the war. His incoherent war policy, combined with the lies and deceptions he employed to sell it, resulted in a loss of public faith in his honesty. He began to doubt himself, while his incompetent administration, exemplified by [[Robert McNamara]], began to have doubts about the morality of US policy. Many of them would join the anti-war movement.