Between 1969 and 1970, recently inaugurated president of the United States (U.S.) Richard Nixon undertook the decision to expand the ongoing war in Vietnam into its neutral neighbour, Cambodia. This was done through a combination of secret bombing campaigns and joint US-South Vietnam operation into Cambodian territories. The expansion of the war into Cambodia was executed to fulfil certain political and military objectives regarding the war in Vietnam pursued by the Nixon Administration. These objectives included eliminating National Liberation Front (NLF) and North Vietnamese Army (NVA) sanctuaries in the border areas to reduce their ability to launch another offensive, demonstrating the effectiveness of the Vietnamization programme through joint US-ARVN military operations. In addition, it was to send signals to both the North Vietnamese policymakers in Hà Nội and its communist allies, the Soviet Union and China, during ongoing peace negotiations held in Paris, of Nixon’s resoluteness in escalating the war when necessary whilst limiting US military losses and fulfilling its withdrawal commitments. Furthermore, Nixon’s Cambodia endeavours had significant implications at home and abroad, which would also be examined in relations to their successes and failures. Hence, it is important to look at the extent to which Nixon’s expansion of the Vietnam conflict into Cambodia achieved its intended objectives. The underlying hypothesis raised here is that Nixon’s expansion of the war into Cambodia failed to achieve most of its maximum military and political objectives but at the same time, he was more temporarily successful in controlling domestic opinions surrounding escalation of the war into Cambodia. The implications were that whilst Cambodia was further destabilised, it also pushed Nixon to pursue options that meant to seek an honourable withdrawal from Vietnam but actually prolonged the war. Hence, this hypothesis will be disseminated throughout the analysis of the question.
Nixon’s decision to expand the Vietnam war into Cambodia in the early 1970s and its implications for the later years of the conflict remained one of the most controversial and important aspects of his turbulent presidency. In terms of secondary literature, the Cambodia episode is covered extensively in the overall historiography of the Vietnam War and is still expanding. In particular, there has been scholarly debates on the outcome of Nixon’s Cambodian endeavours and its impact on on the domestic front and further afield throughout the course of the war. More orthodox historians such as George C. Herring has emphasised on how the escalation into Cambodia limited Nixon’s options to attain his goal of ‘peace with honours by exacerbating the divisions between Nixon and the rest of United States society. It also contributed to further diplomatic deadlock during ongoing peace negotiations with North Vietnam in Paris. Other historians The Orthodox historiography also expanded on the shortcoming of Nixon Cambodian decision in terms of the causation link between U.S. intervention into Cambodia, which made it a part of a wider Indochinese conflict, and the destabilisation of Cambodia, serving as a precursor to its takeover by the Communist Khmer Rouge in 1975 and the genocidal atrocities that followed. At the same time, countering the Orthodox narrative, the revisionist historiography, which is predominantly covered by former civilian and military officials and a few scholars, has put emphasis on the case of the Cambodian episode as one of many ‘lost victories’ on the battlefield in the later years of the Vietnam War that were undermined by U.S. domestic politics. This can be seen in works by Lewis Sorely, which viewed the Cambodian incursion of 1970 as a tremendous military success despite its limitations based on enemy casualties and demonstrating the progress made by Vietnamization through specific case studies of South Vietnamese military commanders. Whilst most of the literature incorporates the Cambodian episode within the larger context of the war in Vietnam itself, a smaller number of works, especially from the likes of William Shawcross, examined Nixon’s venture into Cambodia through providing in-depth analysis of the complexities of Cambodian history, society and geopolitical position in the lead up to the escalation. Thus, providing a broader context to the escalation and putting emphasis on the agency of Cambodian actors during the period whilst reinforcing the popular notion of the aftermath of Nixon’s decision-making as a tragedy for the Cambodian population. To further contribute to the expanding historiography, one would raise the hypothesis to challenge both orthodox and revisionist narrative, that President Nixon’s decision to expand the Vietnam War into Cambodia failed to achieve most of its maximum military and political objectives. On the other hand, he was temporarily more successful in controlling public opinions surrounding his decision, which allowed his domestic reputation to remain intact for the remainder of his presidency. The implications were that whilst it contributed to the further destabilisation of Cambodia as another theatre of a wider Indochinese conflict and removal of its fragile neutrality, it also pushed Nixon to pursue policy options that were meant to seek an honourable withdrawal from Vietnam but in actual fact, prolonged the conclusion of the war with disastrous results. At the same time, to determine the rationality of the decision-making process of the Nixon Administration regarding this aspect of the Vietnam conflict to strengthen the hypothesis.
In order to thoroughly analyse the successes and failures of Nixon’s Cambodian endeavours between 1969 and 1970, it is important to understand the broader context behind the decision. Moreover, the maximum military and political objectives that the Nixon Administration hoped to gain with regards to the war in Vietnam. When Richard Nixon became president in January 1969, he was elected on premise of extricating the United States from its military commitments in Vietnam with its international and domestic prestige remained intact. This was to be done through ‘waging war on all fronts’, which included escalating the conflict in Vietnam into neighbouring countries. The expansion of the war into Cambodia initially started in March 1969 with a secret bombing operation in Eastern Cambodia dubbed MENU with four individual components, BREAKFAST, LUNCH, SNACK, and DESSERT. Eastern Cambodia was part of the Hồ Chí Minh Trail supply system, used by North Vietnam to supply arms and personnel to the front in the South and ran through its two neighbouring countries, Laos and neutral Cambodia. According to Melvin Small, Cambodia was the perfect place for Nixon to weaken North Vietnam and the National Liberation Front (NLF)’s capability to launch military offensives from their Cambodia sanctuaries into the South and to send signals to them that he was willing to escalate without damaging his domestic political prestige. Furthermore, militarily, as requested by general Creighton Abrams, the bombing raids were also to be used to find and eliminate the elusive Central Office for South Vietnam (COSVN), which was used by North Vietnam to influence the military situation in South Vietnam. In addition, in the context of ongoing peace talks that were being held between North Vietnam and the U.S. in Paris, France, the secret bombing operation in Cambodia aimed to coerce the North Vietnamese into negotiating on his terms through demonstrating the willingness to take measures that the previous Johnson Administration would not have taken. At the same time, taking advantage of his previously earned reputation as a hard-line anti-communist in dealing with communist powers, which he dubbed the ‘Madman Theory’. To ensure that the bombings were not constituted as a violation of Cambodia’s sovereignty and neutrality, Small argued that Nixon obtained informal approval from Cambodian leader Prince Sihanouk, who was concerned about North Vietnamese presence, despite with his permission, in his country, and their support for the Khmer Rouge insurgency. Even though there were evidence of Sihanouk’s informal complicity in authorising the operation, William Shawcross maintained that even though Sihanouk permitted the bombardment, he was never asked about a wide-scale B-52 operation and the approval was viewed as uncertain.
Operation MENU lasted from March 1969 into April 1970, in which 3,875 B-52 raids dropped 108,823 tons of bombs into Cambodia. The raids only made short-gain military gains in making it difficult for North Vietnam to deliver supplies to the Southern front but did not reduce the enemy’s war-making capability and instead, it pushed the North Vietnamese further inland into Cambodian territories. At the same time, the existence of the COSVN was proved to be inconclusive. Moreover, the increasing number of civilian casualties led to resentment from the local population and increased support for the indigenous Communist insurgency, the Khmer Rouge, which further contributed to the erosion of Cambodia’s fragile neutrality. Diplomatically, the bombings did not yield extra concessions from North Vietnam in the Paris peace talks, which prolonged the process. Despite so, the domestic impact of the Cambodia bombings was limited by the efforts of the Nixon Administration to maintain its secrecy from members of the public and even members of the Administration. Nonetheless, operation MENU laid the foundation for the escalation of the war in Vietnam into a previously neutral country and became a part of Nixon’s decision-making process.
With the bombings providing the initial stages of escalation, it was the military incursion of 1970 that resulted in most of the controversies surrounding Nixon’s Vietnam policy towards Cambodia and with greater domestic implications. The coup d’état of March 1970 in Cambodia, in which General Lon Nol overthrew Prince Sihanouk and established a pro-U.S. regime, have often been cited as the catalyst for Nixon to undertake the decision to deploy troops into Cambodia. Even so, the possibility of military actions towards Cambodia had been part of the decision-making process of the Nixon Administration since 1969. Early on, the Administration had developed a two-track policy towards Cambodia that involved bombing operations and improving diplomatic relations, which had been strained since 1965. This was based on several factors, which included the Administration’s belief in possibilities of military victories in Vietnam and the need to respond to the realities on the ground in Cambodia, especially NVA and NLF presence in the border areas. Thus, the coup opened the possibility of more drastic military actions due to the deteriorating military and political situation in the country and the establishment of a more U.S.-friendly government in Cambodia. After the coup, the Nixon Administration extended its recognition to the Lon Nol regime and sent in economic and military assistance while the American command in Saigon authorised South Vietnamese (ARVN) military operations against NVA/NLF sanctuaries in the borders by late March. In the context of the wider Vietnam conflict, during this period, the Nixon Administration undertook the Vietnamization programme that it inherited from the Johnson Administration. The programme was designed to increase the combat capability of the ARVN whilst gradually reducing U.S commitments and was in full swing by early 1970, however, real progress was difficult to determine due to the fundamental weaknesses of the ARVN. Thereby, it can be seen that the deteriorating situation in Cambodia and the military imperatives in South Vietnam concerning the sanctuaries would have allowed an opportunity for Nixon to demonstrate the progress made by Vietnamization so far. At the same time, as with the secret bombings, the political change in Cambodia presented Nixon with another opportunity to prove to his Communist adversaries that he was willing to risk escalation whenever possible, which was in line with his ‘Mad Man’ thinking. Hence, to strengthen the U.S.’s bargaining position at the Paris peace talks. Even so, this did not immediately result in a decision for drastic U.S. military intervention into Cambodia. There was a gradual decision-making process towards the incursion by late April 1970. There were varied assessments of the Cambodian situation in the Nixon Administration, within State and Defense Departments. Civilian officials such as State and Defense Secretaries William P. Rogers and Melvin Laird, opposed military action in Cambodia and advocated a return to true neutrality. On the other hand, military officials in the Pentagon, including Kissinger’s deputy, Alexander Haig stressed on the need to aid the poorly trained and equipped Cambodian army and prevent the fall of Cambodia to Communism. Orthodox historians such as Herring have emphasised on Nixon’s insistence on military intervention from the start, which showed an imperative from an insecure individual to show his courage in times of crisis. At the same time, Asaf Siniver further emphasised on how he left out Rogers and Laird out of the decision-making process and preferred to consult with Kissinger and also Haig, in which the cabinet was not informed until the President had made up his mind. On the contrary, Peter G. Drivas argued that Rogers and Laird were not entirely cut out from the decision-making process, while their objections to the military incursion were known to Kissinger and Nixon and attempts were made to keep both cabinet officials ‘in the loop’. Thus, this showed that the decision-making process on Cambodia was not irrational and dictatorial as previously portrayed but it still led to frictions within the Administration.
By late April, Nixon made the decision to launch a military incursion into Cambodia to eliminate NVA/ NLF sanctuaries in the border areas to South Vietnam. The incursion was done in two phases. The first one was to deploy ARVN troops, with U.S. air support, into the Parrot’s Beak section of Cambodia, a small strip of land located thirty-three miles from Saigon. The second phase was a joint U.S.-ARVN operation, dubbed “Toàn Thắng” (Total Victory) to eliminate the elusive COSVN, which the bombing raids had previously failed to do so, in the Fish Hook area and to clear out Communist sanctuaries in the country. During the entirety of the operation, there were 31,000 U.S. and 19,000 ARVN troops, conducting search-and-destroy operations across the border areas throughout May and June. Militarily, the incursion failed to achieve maximum objectives. Revisionist scholars maintained the joint U.S.-ARVN operation disrupted the North Vietnamese supply line and reduced the enemy’s capacity to use Cambodia as a sanctuary. Sorely viewed the Cambodia incursion as amongst the forgotten victories of the Vietnam War, which was limited by political constraints. The results, which Sorely described as ‘impressive’, included significant casualties inflicted on the enemy, 11,349 killed in action with a further 2,328 captured or rallied.The outcome also demonstrated the progress made by Vietnamization through focusing on the personal exploits of several ARVN commanders during the operation in Parrot’s Beak, such as General Nguyen Viet Thanh and General Do Cao Tri. Thus, this would have strengthened argument for improvements made within the ARVN. At the same time, the military results can be seen as significant but limited. This was mainly due to the fact that throughout the operation, the elusive COSVN was never identified and destroyed, which was the main objective of the operation. Furthermore, U.S. and ARVN troops were unable to distinguish between friend and foe, with the latter engaged in raping, lutting and burning, which would have undermined the progress made by Vietnamization. Furthermore, the Communist sanctuaries were not entirely cleared out with the NVA/NLF’s military capability not significantly diminished. This was shown in a CIA study, which concluded that NVA/NLF supplies could be replenished within two or three months. On the diplomatic front, the incursion also failed to make a dent for the U.S. in peace negotiations. Similar to the MENU bombing raids, North Vietnamese policymakers remained oblivious to the ‘Mad Man’ signal sent by Nixon and did not push them to make extra concessions. Furthermore, this also prolonged the peace negotiation process, this also resulted in North Vietnamese negotiators and their NLF allies to cancel a scheduled May 6 meeting of the public talks between each sides and suspension of ongoing secret talks between Kissinger and his North Vietnamese counterpart, Lê Đức Thọ. Therefore, it is shown that the Cambodian incursion of spring 1970 failed to achieve its maximum objectives, militarily and diplomatically, with very limited combat results to show for. The implications of this included the further destabilisation of Cambodia with the Lon Nol regime increasingly dependent on U.S. military support and further delay in the Vietnam peace process.
One of the most controversial aspects of the Cambodian incursion was the U.S. domestic reactions to it. The incursion into Cambodia was made public by President Nixon in a televised address on April 30, 1970. In the televised address, Nixon publically justified the incursion as actions taken to prevent North Vietnamese military aggressions in the border areas whilst respecting the ‘neutrality of the Cambodian people.’ Thus, portraying the North Vietnamese as the aggressor. Furthermore, he also made the link between the incursion and Vietnamization, in which he emphasised on the operation in Parrot’s Beak as ‘exclusively South Vietnamese ground operations under South Vietnamese command’. This would have linked up well with his commitment to ongoing U.S. troop withdrawal, which was mentioned at the start of the address. Furthermore, the address also reinforced the portrayal of Nixon’s insecurity in demonstrating his courage through the use of various historical analogies of decisions made by past Presidents during times of conflict. The Cambodia decision and public address resulted in unfavourable domestic reactions at unprecedented proportions, within the Administration and the wider public. Within the Administration, three of Kissinger’s top aides in the National Security Council (NSC) resigned in protest. At the same time, two hundred and fifty Foreign Service officers signed a letter of protest addressed to State Secretary Rogers. The incursion also reignited the anti-war movement, with protests exploded across university campuses. The most notable of these were in May 1970 at Kent State University in Ohio and Jackson State in Mississippi, in which confrontations with national guardsmen and state police resulted in the deaths of several students. This led to further domestic uproars. Furthermore, at legislative levels, Senators Sherman Cooper and Frank Church proposed an immediate amendment that would cut off all military funding for operations in Cambodia after June 30. Senators Mark Harfield and George McGovern went further by proposing another amendment to the military appropriation bill that was under consideration in the Senate that would end all funding the war after December 31 and require the immediate withdrawal of all U.S. forces by June 30 of 1971. Whilst the domestic reactions to the Cambodia incursion were overwhelmingly negative, the Nixon Administration was arguably more successful in limiting domestic opposition surrounding its actions. When he undertook the decision to invade, he and his advisors were fully of the domestic backlash once it was made public. This was shown during the invasion of Cambodia, more than a majority of those polled continued to support Nixon’s Vietnam policies but most of the opposition came from students, the media and Congress. At the same time, the two aforementioned amendments, whilst symbolic of Congress’s opposition to the Administration’s Vietnam policies, failed to pass in Congress and did not lead to significant changes in policies regarding the war. It is important to be aware that Nixon would have withdrew anyway from Cambodia by the end of June, which he announced on May 8. Moreover, through a number of public relation overtures, Nixon was able to appeal to what was dubbed the ‘Silent Majority’ in his November 1969 address for support. This was shown by violent and unprovoked attacks by several hundred construction workers on anti-war protestors on May 8 and a pro-Nixon demonstration held on May 20 by a hundred thousand “hard-hats”, reflecting working class conservativism. Furthermore, by July 1970, 58 percent of polled Americans blamed the student themselves for what happened at Kent State. These attempts Nixon’s domestic credibility to remain intact despite the controversial nature of the Cambodia operation. Even so, the implications of the domestic backlash were that it led to further rift within U.S. society as a whole and increased scrutiny to Nixon’s Vietnam policies within Congress throughout the remainder of his presidency.
In general, the decisions undertaken by the Nixon Administration to expand the Vietnam War into Cambodia between 1969 and 1970 failed to achieve their maximum military and political objectives with significant implications for Cambodia and the wider war in Vietnam. On the other hand, the Administration was more successful in limiting the domestic backlash regarding the Cambodia decisions. The Cambodia decisions, including the 1969 MENU bombing raids and U.S. — ARVN military incursion of April 1970 in the border areas, failed to achieve its military objectives. Whilst inflicting limited damages on their Communist adversaries, they failed to disrupt the NVA/NLF’s supply line into South Vietnam in the border areas and were unable to identify and eliminate the elusive COSVN, whose existence was never proven. Moreover, the incursion did not successfully demonstrate the progress made with Vietnamization. Politically, despite their ‘Mad Man’ intentions, they failed to extract extra concessions from North Vietnam in the Paris peace negotiations and even contributed to the diplomatic deadlock. The implications were the further destabilisation of Cambodia and increased support for the communist Khmer Rouge insurgency. Domestically, the incursion led to significant backlash within government and the wider public. This was shown by resurgence of anti-war protests and opposition within Congress. Even so, their impact was successfully temporarily reduced by the Administration’s public relation overtures, which allowed its domestic credibility to remain intact. At the same time, this led to further division in society and reduced faith in the Administration’s handling of ending the war in Vietnam.
 George C. Herring, America’s longest war: the United States and Vietnam, 1950–1975 (Boston: McGraw-Hill Education, 2014): pp. 303–304.
 Gary R. Hess, Vietnam: Explaining America’s Lost War (Chichester, West Sussex: Wiley Blackwell, 2015): pp. 195–197.
 Lewis Sorely, A Better War: The Unexamined Victories and Final Tragedy of America’s Last Years in Vietnam (New York: Harcourt Brace & Co, 1999): pp. 210–211.
 William Shawcross, Sideshow- Kissinger, Nixon, and the Destruction of Cambodia (New York: Cooper Square Press, 2002): p. 51.
 Lien-Hang T. Nguyen, “Waging War on All Fronts: Nixon, Kissinger, and the Vietnam War, 1969–1972,” in Nixon in the World: American Foreign Relations, 1969–1977, ed. Fredrik Logevall and Andrew Preston (Oxford: Oxford University Press, 2008): p. 185.
 Herring, America’s longest war, p. 283.
 Melvin Small, The Presidency of Richard Nixon (Lawrence: University Press of Kansas, 1999): p. 71.
 Alexander J. Banks, “Britain and the Cambodian Crisis of Spring 1970, “Cold War History 5, no. 1 (2005): p. 89.
 Herring, America’s longest war, p. 283.
 Small, The Presidency of Richard Nixon, p. 61.
 Ibid, p. 71.
 Shawcross, Sideshow, p. 94.
 Ibid, p. 72.
 Peter G. Drivas, “The Cambodian Incursion Revisited,” International Social Science Review 86, no. 3 & 4 (Fall-Winter 2011): p. 138.
 Jeffrey Kimball, Nixon’s Vietnam War (Lawrence: University Press of Kansas, 1998): p. 199.
 Herring, America’s longest war, pp. 293–294.
 Asaf Siniver, Nixon, Kissinger, and U.S. Foreign Policy Making: The Machinery of Crisis (Cambridge: Cambridge University Press, 2008): p. 83.
 Siniver, Nixon, Kissinger, and U.S. Foreign Policy Making, p. 82.
 Ibid, p. 83.
 Herring, America’s longest war, pp. 299.
 Siniver, Nixon, Kissinger, and U.S. Foreign Policy Making, p. 83.
 Drivas, “The Cambodian Incusion Revisited,” p. 150.
 Carolyn Eisenberg, “Remembering Nixon’s War,” in A Companion to the Vietnam War, ed. Marilyn B. Young and Robert Buzzanco (Malden: Blackwell Publishers, 2002): p. 266.
 Nguyen, “Waging War on All Fronts,” p. 193.
 Kimball, Nixon’s Vietnam War, p. 210.
 Hess, Vietnam, p. 188.
 Sorley, A Better War, p.210.
 Ibid, pp. 210–211.
 Shawcross, Sideshow, p. 150.
 Ibid, p. 151.
 Kimball, Nixon’s Vietnam War, p. 224.
 Ibid, p. 224.
 Richard Nixon, “139 — Address to the Nation on the Situation in Southeast Asia” (speech, Washington, DC, April 30, 1970), The American Presidency Project, http://www.presidency.ucsb.edu/ws/?pid=2490.
 Nixon, “139- Address to the Nation.”
 Lloyd Gardner, “The Last Casualty? Richard Nixon and the End of the Vietnam War, 1969–1975,” in A Companion to the Vietnam War, ed. Marilyn B. Young and Robert Buzzanco (Malden: Blackwell Publishers, 2002): p. 246.
 Small, The Presidency of Richard Nixon, p. 79.
 Gardner, “The Last Casualty?” p. 246.
 Nguyen, “Waging War on All Fronts,” p. 194.
 Andrew L. Johns, Vietnam’s Second Front: Domestic Politics, the Republican Party, and the War (Lexington: University Press of Kentucky, 2010): p. 284.
 Small, The Presidency of Richard Nixon, p. 80.
 Johns, Vietnam’s Second Front, pp. 288–289.
 Siniver, Nixon, Kissinger, and U.S. Foreign Policy Making, p. 87.
 Small, The Presidency of Richard Nixon, p. 82.
- Primary source:
Nixon, Richard. “139 — Address to the Nation on the Situation in Southeast Asia.” Speech, Washington DC, April 30, 1970. The American Presidency Project. http://www.presidency.ucsb.edu/ws/?pid=2490.
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Drivas, Peter G. “The Cambodian Incursion Revisited.” International Social Science Review 86, no. 3 & 4 (Fall-Winter 2011): 134–152.
Eisenberg, Carolyn. “Remembering Nixon’s War.” In A Companion to the Vietnam War, edited by Marilyn B. Young and Robert Buzzanco. Malden: Blackwell Publishers, 2002.
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Herring, George C. America’s longest war: the United States and Vietnam, 1950–1975. Boston: McGraw-Hill Education, 2014.
Hess, Gary R. Vietnam: Explain America’s Lost War. Chichester, West Sussex: Wiley Blackwell, 2015.
Johns, Andrew L. Vietnam’s Second Front: Domestic Politics, the Republican Party, and the War. Lexington: University Press of Kentucky, 2010.
Kimball, Jeffrey. Nixon’s Vietnam War. Lawrence: University Press of Kansas, 1998.
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Shawcross, William. Sideshow- Kissinger, Nixon, and the Destruction of Cambodia. New York: Cooper Square Press, 2002.
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