Agent Orange in Laos:

Documentary Evidence


 By Andrew Wells-Dang

Expanded version, August 2002


 The 1962 Geneva Accords proclaimed Laos a neutral country and forbade outside military involvement there. As the war in Vietnam escalated, however, neither the US nor North Vietnam was able to resist intervening. Local Laotian revolutionaries and their Vietnamese allies built a network of paths along the border, later termed the “Ho Chi Minh Trail,” and covert US operations used every means available to try to stop them. One of the earliest of these efforts, Operation Tiger Hound, began in November 1965 and set out to “combine in one program [all] the air tactics and techniques developed thus far in Laos and South Vietnam.”


Among these methods was “defoliating jungle growth along selected routes,” using herbicides such as Agent Orange “to improve visibility.” Already being sprayed in South Vietnam, herbicides had a military purpose of clearing land around roads and trails so that enemy movements could be detected and stopped. The environmental and human consequences never entered the calculation; nor, with few exceptions, did the international legality of spraying ever trouble American leaders. By far the greater concern was preservation of secrecy, in case evidence of chemical use might be turned to Communist propaganda advantage.

 The primary tactic in the “secret war” was bombing, which caused immense damage in almost every province of Laos. The use of herbicides, a sideshow to a sideshow, was reported on during the conflict but officially denied until 1982, when Air Force historian William Buckingham’s draft of the Operation Ranch Hand study was made public under a Freedom of Information Act request by the National Veterans Task Force on Agent Orange. In a subsequent New York Times interview, former US Ambassador William Sullivan said that “secret” was not the right word to describe the herbicide program: “Rather, it was not admitted or confirmed.”

 In response to a November 1969 Congressional query, the Military Assistance Command-Vietnam provided a classified summary of 434 sorties in Laos from flight records beginning on December 3, 1965 and ending September 7, 1969. Additional mission reports from the HERBS database, made public through the Environmental Support Group, continue until October 1, 1970. In total, missions were flown on 209 dates, spraying 537,495 gallons—a figure that is surely incomplete, but already significant, though far short of the approximately 21 million gallons sprayed on South Vietnam.

 Air Force spraying was heaviest during the first half of 1966, with more than 200 sorties spraying approximately 200,000 gallons of Agent Orange.[i][6] Spraying continued at a relatively rapid rate until February 1967, when with the exception of one mission listed in May 1967 it ceased until November 1968. Buckingham’s Ranch Hand study lists a condensed version of spraying over the same period, totaling 419,850 gallons over 163,066 acres. Agent Orange was the primary herbicide used (about 75%), followed by Agents Blue (15%) and White (10%).

 No complete list of targets and locations has been found; detailed records from some periods have been handed over to the demining agency, UXO Lao, while others may be scattered in military archives. The limited number of maps and coordinates found at the National Archives suggest that the greatest concentration of spraying occurred north and south of the Demilitarized Zone near the Vietnamese border in Savannakhet and Attapeu provinces. After the chemicals had been applied for 1-2 weeks, fighter-bombers would return to strike any targets revealed in the area.

 Declassified documents do record the aircraft used for Air Force operations: mostly C-123s from the Ranch Hand operations in South Vietnam, as well as a limited number of F-4s. Both types were flown from Bien Hoa air base as well as off ships in the South China Sea. At one point, military authorities proposed establishing a Thailand-based spray capability;[ii][10] whether this ever occurred is unknown, although herbicide tests were conducted at Thai air bases as early as 1964-65.


 As with bombing runs on North Vietnam, Laos was also a secondary target: on at least one occasion in October 1966, when adverse weather conditions hampered spraying near the DMZ in South Vietnam, Operation Ranch Hand’s planes sprayed Laos instead. A January 1969 memo from the Chemical Operations Division at MACV headquarters in Saigon notes that “the legality of these out-of-country operations is uncertain” and cites increasing risks from ground fire near the DMZ. The author, Maj. Gen. Elias Townsend, recommends that herbicides be used only in “high risk” areas and in conjunction with “suppressive fighter attacks.” As the bombing of Laos increased dramatically after the “bombing pause” on North Vietnam starting in late 1968, the role of herbicides in Laos declined, as they fell short of the total war the US was beginning to wage.

 The use of herbicides was quickly expanded to the destruction of enemy crops. Citing effective use in South Vietnam, Gen. William Westmoreland first proposed crop destruction in Laos in May 1966. Records from MACV list 64 crop destruction missions in Laos from September 1966-September 1969, targeting a total of 20,485 acres. Agent Blue was the most frequently used chemical on these flights. US Admiral McCain later attributed part of Gen. Vang Pao’s short-lived 1969 capture of the Plain of Jars to crop destruction missions there. And after the Lao government banned opium cultivation in 1971, herbicides were used to destroy hilltribe poppy crops as late as 1974. One mission report from 1969 describes “a highly successful attack on enemy rice crops in North Laos…almost four thousand acres destroyed just before harvest.” One wonders if the “enemy rice crops” were able to fight back.

 The “experimental” use of herbicides outside of South Vietnam had been under consideration by the Department of Defense since October 1962 for a broad, undefined area around “the Cambodian-Laotian-North Vietnam border”—a difficult task given that Cambodia and North Vietnam had no common border, with several southern Laotian provinces in between. This excessive plan was never implemented in full, but it gives a sense of what was to follow.

 Ambassador Sullivan expressed nervous opposition at first, citing “allegations concerning earlier [US] uses of chemical weapons in Laos.” Exactly what those allegations were is unclear, but they presumably refer to chemicals other than herbicides. The increasing sense of alarm over the movements of personnel and materials along the “Ho Chi Minh Trail,” however, soon removed his scruples over the program. Sullivan recognized that interdiction would require “massive amounts of defoliants,” along with “Washington discussion at high levels,” since herbicide use “would involve the overt violation of the 1962 agreements on Laos.”

 In November 1965, soon before the Air Force spraying program was to begin, Sullivan wrote in a memo to Washington, “I am convinced that our efforts in Laos, particularly along infiltration route, are critical to US forces engaged in South Vietnam…We can carry on these efforts only if we do not, repeat do not, talk about them, and when necessary, if we deny that they are taking place.”

 Not everyone followed the ambassador’s suggestions. The first stories in the US press broke in December 1965. In February 1966, the Washington Post and New York Times ran stories on defoliation operations in Laos, claiming that 12-16 UC-123s had been diverted from the Ranch Hand program in Vietnam. To the State Department’s consternation, the Times quoted one American official in Saigon saying, “We’re going to turn the Ho Chi Minh Trail brown. We’re mounting a maximum effort over there every day.” A telegram from Gen. William Westmoreland later that year put the same message in more formal language: “During all phases, there will be an intensification of psychological warfare and herbicide operations…through the Laotian Panhandle…We must use all assets at our disposal to block, deny, spoil and disrupt this infiltration.”

 Former chief Air Force historian Richard Kohn claims that spraying in Laos took place “with the permission of the Laotian government” headed by then-President Souvanna Phouma. However, archival documents make it clear that Ambassador Sullivan and other officials provided very little specific information to the Lao, who may have preferred to remain uninformed of the details of covert US operations carried out in their country. Sullivan wrote to the State Department in August 1965 that “Much of what we are now doing in the [Ho Chi Minh Trail] corridor is known only in vague outline to Souvanna and I’m sure he prefers it that way. Later, however, Assistant Secretary of State Bundy wrote to Acting Secretary Ball that Prime Minister Souvanna specifically requested the use of herbicides.

 Congress was also kept in the dark. When details of the “secret war” first began to emerge in 1969, Sen. William J. Fulbright told Amb. Sullivan, by then promoted to State Department undersecretary, that “this is not the way to do business…I do not really see any justification for keeping [operations in Laos] secret from the American people. At the same hearing, however, the cover-up continued, as the US air attaché in Laos, Col. Robert Tyrell, testified that the reconnaissance and defoliation flights conducted almost daily since 1965 were flown “on occasion.” When asked specifically about herbicides, Tyrell answered, “I believe that since I returned to Laos in June of last year [1968] we have had four defoliation missions. In fact, there had been at least 19.

 Whether defoliation continued after 1970 remains an open question. As a result of increased public outcry, restrictions began to be placed on herbicide use by the US military. In March 1971, Secretary of Defense Melvin Laird requested that he personally approve any herbicide operations in “Laos, Cambodia, or Thailand. Air Force records show that UC-123 planes, whose sole purpose had been listed as “defoliation,” conducted 860 sorties over Laos from January-June 1971, but no further details are given.

 All of the above data refers only to spraying carried out by the US Air Force using fixed-wing aircraft. It may not be a complete record even of these operations, although the start and end date can be confirmed by multiple sources in the declassified record. What is not included here is any spraying conducted by helicopter or directly from the ground. Both the Air Force as well as other units had this capability.

 Also unconfirmed is herbicide use by Air America or the CIA, whose records are still closed. In an April 1968 interview, the vice-president of Air America declared that his company had been contracted by the Department of Defense to defoliate vegetation in Vietnam, Laos, and southern Thailand, based from the Udon Thani airbase. The 1971-3 opium destruction missions were probably carried out on this basis, and secondary sources also report that the CIA had spray mission capability. Air Force records do not list any UC-123 aircraft at Udon Thani during this period, suggesting that other aircraft might have been used; however, 7 UC-123’s were present at the Nakhon Phanom airbase in 1970 and 1971, presumably for defoliation purposes. Further research is needed to confirm the extent of additional herbicide use in Laos.


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