maneuvered Ky and cemented his grip on power in fraudulent elections in 1967 and 1971.
To support South Vietnam's struggle against the communist insurgency, the United States began increasing its contribution of military advisers, using the controversial 1964 Tonkin Gulf incident as a pretext for such intervention. US forces became embroiled in ground combat operations in 1965, and at their peak they numbered more than 500,000. Communist forces attacked major targets in South Vietnam en masse during the 1968 Tet Offensive, and although their campaign failed militarily, it shocked the American establishment, and turned US public opinion against the war. Communist forces supplying the Vietcong carried supplies along the Ho Chi Minh trail, which passed through Laos and Cambodia. US presidents Lyndon Johnson and Richard Nixon authorized Operation Commando Hunt and Operation Menu, SAC bombing campaigns in Laos and Cambodia, about which only high-ranking Congressional officials were informed.
Its own casualties mounting, and facing opposition to the war at home and condemnation abroad, the US began withdrawing from ground combat roles according to the Nixon Doctrine; the process was subsequently called Vietnamization. The effort had mixed results, ultimately failing to stabilize South Vietnam. The Paris Peace Accords of 27 January 1973 formally recognized the sovereignty of Vietnam "as recognized by the 1954 Geneva Agreements." Under the terms of the accords, all American combat troops were withdrawn by 29 March 1973. Limited fighting continued, before North Vietnam captured the province of Phuoc Long in December 1974 and started a full-scale offensive, culminating in the Fall of Saigon on 30 April 1975. South Vietnam briefly came under the nominal rule of a Provisional Revolutionary Government while under military occupation by North Vietnam. On 2 July 1976, North and South Vietnam were merged to form the Socialist Republic of Vietnam. The war left Vietnam
