According to the data, the air force began bombing the rural regions of Cambodia along its South Vietnam border in 1965 under the Johnson administration; this was three and a half years earlier than previously believed.

From the onset of hostilities in South Vietnam and the Kingdom of Laos in the early 1960s, Cambodia's Prince Norodom Sihanouk had maintained a delicate domestic and foreign policy balancing act.

[3] In 1966, Sihanouk made an agreement with Zhou Enlai of the People's Republic of China that would allow PAVN and VC forces to establish base areas in Cambodia and to use the port of Sihanoukville for the delivery of military material.

Beginning in 1967, President Lyndon B. Johnson authorized covert reconnaissance operations by the Military Assistance Command, Vietnam Studies and Observations Group (MACV-SOG).

He had already considered a naval blockade of the Cambodian coast, but was talked out of it by the Joint Chiefs of Staff (JCS), who believed that Sihanouk could still be convinced to agree to ground attacks against the base areas.

Nixon became even more angered when the communists launched rocket and artillery attacks against Saigon, which he considered a violation of the "agreement" he believed had been made when the US halted the bombing of North Vietnam in November 1968.

Nixon, who was en route to Brussels for a meeting with North Atlantic Treaty Organization (NATO) leaders, ordered Kissinger to prepare for airstrikes against PAVN/VC base areas in Cambodia as a reprisal.

The bombings were to serve three purposes: they would show Nixon's tenacity; they would disable the PAVN's offensive capability to disrupt the US withdrawal and Vietnamization; and they would demonstrate US determination, "that might pay dividends at the negotiating table in Paris.

[14] Public opinion polls in 1968–1969 showed the majority of the American people supported the strategy of seeking a diplomatic solution to the Vietnam War via the Paris peace talks.

On 16 March, Nixon summoned Kissinger, Laird, Rogers, and Wheeler to a meeting at the White House to announce that he decided that bombing Cambodia was the "only way" to make North Vietnam compromise because he felt he had "to do something on the military front...something they will understand".

[18] In his diary in March 1969, Nixon's chief of staff, H. R. Haldeman, noted that the final decision to carpet bomb Cambodia "was made at a meeting in the Oval Office Sunday afternoon, after the church service."

In order to prevent criticism of the bombing, an elaborate dual reporting system of the missions had been formulated during the Brussels meeting between Nixon, Haig, and Colonel Sitton.

[31] Sihanouk told US diplomat Chester Bowles on 10 January 1968, that he would not oppose American "hot pursuit" of retreating North Vietnamese troops "in remote areas [of Cambodia]", provided that Cambodians were unharmed.

Nixon was furious when he heard the news and ordered Kissinger to obtain the assistance of FBI Director J. Edgar Hoover to discover the source of the leak.

[18] The administration was relieved when no other significant press reports concerning the operation appeared, and the revelation of the secret bombing of Cambodia did not cause any public outrage.

[18] Likewise, Congressman John Conyers wrote that the Operation Menu bombings led Nixon and his staff to become "enmeshed in the snare of lies and half-truths they themselves had created".

[37] Conyers wrote that Nixon's belief that any action done by the president was justified in name of national security, first asserted with Operation Menu, created the mindset that led him directly to the Watergate scandal.

They were Senators John C. Stennis (MS) and Richard B. Russell, Jr. (GA), and Representatives Lucius Mendel Rivers (SC), Gerald R. Ford (MI), and Leslie C. Arends (IL).

That changed in December 1972, when Major Knight wrote a letter to Senator William Proxmire (D, WI), asking for "clarification" of U.S. policy on the bombing of Cambodia.

[40] Proxmire's questioning led to hearings of the Senate Armed Services Committee, which eventually demanded that the Department of Defense turn over all records of US air operations in Cambodia.

The Department of Defense estimated that the six areas bombed in Operation Menu (Breakfast, Lunch, Dinner, Snack, Dessert, and Supper) had a non-combatant population of 4,247.

[46] The constitutional issues raised at the hearings became less important when the House Judiciary Committee voted (21–12) against including the administration's falsification of records concerning Menu in the articles of impeachment leveled against President Nixon.

[citation needed] It certainly cost North Vietnam the effort and manpower to disperse and camouflage their Cambodian sanctuaries to prevent losses to further air attack.

"[52] Author William Shawcross and other observers asserted that the "Khmer Rouge were born out of the inferno that American policy did much to create" and that Sihanouk's "collaboration with both powers [the United States and North Vietnam] ... was intended to save his people by confining the conflict to the border regions.

The fact is that we were bombing North Vietnamese troops that had invaded Cambodia, that were killing many Americans from these sanctuaries, and we were doing it with the acquiescence of the Cambodian government, which never once protested against it, and which, indeed, encouraged us to do it.

I may have a lack of imagination, but I fail to see the moral issue...[55]The simultaneous rise of the Khmer Rouge and the increase in area and intensity of U.S. bombing between 1969 and 1973 has incited speculation as to the relationship between the two events.

Ben Kiernan, Director of the Genocide Studies Program at Yale University, said the following: Apart from the large human toll, perhaps the most powerful and direct impact of the bombing was the political backlash it caused ...

The CIA's Directorate of Operations, after investigations south of Phnom Penh, reported in May 1973 that the communists there were successfully 'using damage caused by B-52 strikes as the main theme of their propaganda' ...

[58] When Phnom Penh was under siege by the Khmer Rouge in 1973, the US Air Force again launched a bombing campaign against them, claiming that it had saved Cambodia from an otherwise inevitable communist take-over and that the capital might have fallen in a matter of weeks.

By 1975, President Ford was predicting "new horrors" if the Khmer Rouge took power, and calling on Congress to provide additional economic, humanitarian, and military aid for Cambodia and Vietnam.