Between 1966 and 1970, this system operated in the same manner and served the same purposes as the much better known Ho Chi Minh trail (the Truong Son Road to the North Vietnamese) which ran through the southeastern portion of the Kingdom of Laos.

[1] During the next ten years, while the conflicts in neighboring Laos and South Vietnam heated up, Sihanouk managed to sustain his delicate domestic political balance while at the same time maintaining his nation's neutrality (guaranteed by the 1954 Geneva Conference that ended the First Indochina War).

[2] This was no small accomplishment considering that Cambodia was wedged between its perennial enemies: Thailand to the west and South Vietnam to the east, both of whom were increasingly supported by the United States.

[citation needed] Sihanouk came to believe that communist triumph in Southeast Asia was inevitable and that Cambodia's military was incapable of defeating the North Vietnamese, even with U.S. support.

[4]: 296 After direct American intervention in 1965, the increased presence of U.S. naval vessels in coastal waters under Operation Market Time nullified the seaborne route into South Vietnam.

[7] These base areas also served as sanctuaries for PAVN/VC troops, who simply crossed the border from South Vietnam and then rested, reinforced, and refitted for their next campaign in safety.

[citation needed] During 1965 the PAVN had already begun construction of new supply routes to connect the segments of the Ho Chi Minh Trail that ran through southern Laos and into Cambodia.

[8] Although the U.S. command in Saigon and the politicians in Washington became increasingly aware of this arrangement during 1966–1967, they declined to overtly interfere due to the political ramifications of conducting military operations against a neutral country and the wishes of Sihanouk.

[10] In April 1967 the U.S. headquarters in Saigon finally received authorization to launch Daniel Boone, an intelligence gathering operation conducted by the secretive Military Assistance Command, Vietnam Studies and Observations Group or SOG.

[11] The reconnaissance teams that "hopped the fence" into Cambodia were under strict orders not to engage in combat and to covertly collect intelligence on the base areas and PAVN activities.

The result of this effort was Project Vesuvius, in which the American command collated the gathered intelligence on PAVN/VC violations of Cambodian neutrality and presented it to Sihanouk in hopes of altering his position.

[12] By 1968 the Americans were well aware of the scope and scale of the Cambodian logistical effort, but still remained reluctant to overtly violate Cambodia's neutrality since the U.S. still hoped to persuade Sihanouk to come on board against the communists.

[citation needed] With the election of President Richard M. Nixon in 1968 and the announcement of the new American policy of Vietnamization in 1969, America's relations with Cambodia began to change.

[7]: 93–4  He was under pressure from the U.S. to reopen diplomatic ties and to act militarily against the sanctuaries; from the North Vietnamese, who now received 80 percent of their supplies for their southernmost operations through Sihanoukville; and from the fledgling Chinese-supported Khmer Rouge (approximately 4,000 men).

By the summer he created a right-wing Government of National Salvation under General Lon Nol and he suspended North Vietnamese arms shipments through his ports.

[citation needed] On 18 March 1970, taking advantage of a visit by Sihanouk to Moscow and Beijing, the prince was deposed by the National Assembly, who promptly announced the creation of the Khmer Republic.

[3]: 605–6  In the wake of the removal of Sihanouk, the Lon Nol government turned over captured documents to the U.S. disclosing the full extent of his participation in the infiltration effort.

[1]: 98 Nixon was more than willing to seize the advantage offered by the ousting of Sihanouk and the opportunity to strike the border sanctuaries as a means of buying time for both the U.S. and South Vietnam.

The program was quickly superseded by Operation Freedom Deal, the overt support of FANK forces by B-52 and tactical airstrikes by American and South Vietnamese aircraft.

[1]: 96  As far as the long-term repercussions, there were three, all detrimental to the American cause: increased antiwar sentiment in the U.S., which would eventually lead to the fall of South Vietnam in 1975; the beginning of outright support of the Khmer Rouge by the North Vietnamese (who despised and distrusted their Chinese-supported comrades); and the spreading of general war throughout Southeast Asia.

[7]: 247 On 20 August 1971, Lon Nol (now president) launched Operation Chenla II in an effort to open communications between Phnom Penh and the nation's second largest city, Kompong Thom.

[5]: 12–3 On 28 January 1973, the day the Paris Peace Accords took effect, Lon Nol announced a unilateral cease-fire, which the Khmer Rouge promptly ignored, claiming that it was "a deception engineered by the U.S. imperialists and their allies.