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November/December 2018

Secret Warfare: Herbicide Use in Thailand, Laos, and Cambodia

For nearly fifty years, thousands of gallons of ink have been used to write billions of words about the exposure of American troops to herbicides in Vietnam. Much also has been written about the subsequent birth defects in the children of those men and women. This article is by one veteran whose exposure to herbicides has had a severe impact on the health of his three sons.

Some legislative attempts have resulted in laws requiring the VA to treat, compensate, and otherwise help us—and, in a limited sense, to help children afflicted with one birth defect: spina bifida. And that, only after a nearly six-year effort to address a multitude of herbicide-caused birth defects in our children.

But virtually nothing has been done to help veterans exposed to those same herbicides outside of Vietnam, including in the South China Sea where thousands of Navy and Marine Corps personnel served and were exposed—just like those who had boots on the ground in Vietnam.  

Others were affected in Thailand, Cambodia, Laos, the Philippines, Okinawa, Guam, and a virtually unknown place—Johnston Atoll. This article focuses on Thailand, with special attention to Laos and Cambodia.

Legislative efforts are underway in the House and the Senate to very belatedly recognize the service of American veterans and their exposures in Thailand. In the Senate, S.2105 was introduced in November 2017, while H.R.4843 was introduced in the House the following January. Both bills contain identical wording and have been referred to the Veterans’ Affairs Committees in their respective chambers. No hearings or additional actions have been scheduled. As of August 7, S.2105 was co-sponsored by seventeen senators, and H.R.4843 had thirty-five co-sponsors.

We all know and pretty much understand what herbicides—commonly referred to as Agent Orange—are, and we know about their adverse health impacts on humans. Likewise, many are familiar with the defoliation program known as Operation Ranch Hand. So we’re not going to rehash those topics, but will focus on the refusal of our government to officially recognize and right a long-standing wrong perpetrated against veterans who served in Thailand supporting the war in Vietnam.

Vietnam and Thailand were combat zones. Both countries had similar Rules of Engagements. Although most of the Air Force bases in Thailand were staging areas for operations all over Vietnam, American military personnel in Thailand also were subjected to aggressive, repeated attacks from communist sympathizers. In its 1968 Contemporary Historical Examination of Current Operation (CHECO) Project Southeast Asia report, Attack on Udorn, the Air Force noted that Thailand was a “prime target of Communist expansion, and the intensified awareness of the Communists was exacerbated by the Air Force presence.” The Department of Defense had legitimate concerns about the threat to U.S. personnel and equipment in Thailand, which led to the use of herbicides inside base perimeters as a means of preventing enemy incursions. Throughout this article, we will refer to the sixty-odd CHECO reports we’ve discovered.

The parallels between base defense methods in Vietnam and Thailand were highlighted in the 1969 CHECO Report, 7AF Local Base Defense Operations: July 1965 to December 1968. This report provides an overview of Air Force base operations. It focuses on the heightened risk of attacks against air bases because they presented the enemy with a “concentration of worthwhile targets.” Additionally, the report states: “Thailand is going through the same growing pains experienced in the Republic of Vietnam, but the knowledge and experience gained in the development of air base defense in Vietnam permits a more rapid development in Thailand.” Similar tactics and procedures in base defense were used in both countries because the bases faced the same threats.

The Rules of Engagement provided permission for—and limits on—the use of herbicides throughout Southeast Asia. A MACV directive in 1966 highlighted the procedure for requesting aerial spray, power spray, and hand spray in Vietnam. That mandate empowered the MACV Commander and the U.S. Ambassador to approve herbicide operations. The decree also delegated authority to approve defoliation requests using hand spray and ground-based power spray. It emphasized U.S. assistance to local governments in requesting, supplying, and executing defoliation operations. Thailand’s close coordination with Operation Ranch Hand meant that its bases also received a steady supply of herbicides.

Throughout the war in Vietnam, Ranch Hand UC-123K aircraft were dispatched from airbases in Thailand—including Ubon, Udorn, NKP, and Takhli—on many occasions to carry out missions against targets in Vietnam and Laos. During late 1968 and early 1969, Ranch Hand aircraft conducted herbicide missions out of Udorn. In mid-January 1969 seven Ranch Hand aircraft flew to Ubon to conduct an attack against a “special target” in Laos. Again, in early February 1969, Ranch Hand flew Laos missions from Udorn.

In a one-week period in August 1969, Udorn was the departure point from which Ranch Hand aircraft flew twenty-eight sorties from Thailand to target Laotian crops with Agent Blue using five UC-123Ks. The Ranch Hand History Project notes that an airman who worked on Operation Ranch Hand received a letter of commendation for his actions in Thailand during those missions. National Archives records list herbicide missions that originated in Thailand in 1966, 1967, 1969, and 1970. Even though these missions were classified, they clearly show the coordination between the U.S. military in Thailand and Operation Ranch Hand.

Air Force documents confirm that herbicide deliveries apart from Ranch Hand were transported to and from Thailand. National Archives records show that herbicides were transported from Vietnam to Takhli in 1973. This reporting correlates with other 1973 Air Force documents showing that civil engineers had developed a standard operating procedure for the use of herbicides on Takhli to prevent mishandling. These records seem to indicate that the movement of herbicides to and from Thailand was not exclusively associated with Ranch Hand missions and that herbicides were routinely applied throughout Thailand.

Because the spray apparatus on Ranch Hand aircraft and the 55-gallon barrels containing herbicides were known to leak, the risk of exposure on the flight lines and in storage areas on Thai bases was heightened. One airman stationed at Ubon from 1969-72 said that he helped load barrels of Agent Orange onto UC-123Ks during the first part of his tour. He also noted in a sworn statement that the barrels “were leaking all the time,” and the herbicide spilled all over his uniform and hands.

Another veteran’s appeal to the Board of Veterans’ Appeals asserted that he was a material handler of Agent Orange during his time at Ubon in 1968-69. He, too, said that the barrels often leaked. Leakage from nearly empty herbicide barrels was constant because it was difficult to drain the last two or three gallons. The color distortion caused by leaking barrels containing herbicides is clearly shown in photographs of herbicides stored on Johnston Atoll. The herbicides stored there, brought in after the war in Vietnam ended in 1975, allegedly were burned at sea around 1977.

Due to increased, ongoing security concerns, Air Force leadership ordered the use of other herbicides. Several documents demonstrate that Agents Orange and Blue were present in Thailand. Records show that 28,000 gallons of herbicides were flown by two C-130s from Phu Cat Airbase to Udorn prior to Ranch Hand missions launched from Udorn to targets in Laos from February 2-7, 1969.

As noted in the 1971 CHECO Report, only 7,000 gallons of this herbicide, mostly Agent Orange, were applied in Laos, leaving 21,000 gallons unaccounted for at their last-known location in Thailand. Air Force documents show that defoliation operations around the Udorn perimeter took place around the same time. It stands to reason that this remaining herbicide was used on other bases since 21,000 gallons was far more than necessary for a single base. Hence, herbicides, including Agent Orange, were used extensively in Thailand despite a decades-long VA denial of claims of service-connected exposure by veterans with service in Thailand.

The prevalent use of herbicides in Thailand is further documented by the U.S. Embassy’s approval of their use on several occasions. In 1972 vegetation control at Korat was a serious concern: Dense growth could provide the enemy access to the KC-135 storage area. So the embassy approved the use of herbicides. Additionally, the 1973 CHECO Report states that soil sterilization and herbicide use were approved by the embassy in 1969.

These admissions correlate with sworn affidavits from several airmen. Historical reports establish that a squadron in 1971 “began spraying chemical herbicides on the unmanageable plant life.” In 1972 the leadership at U-Tapao sought to “expand herbicide use” in clearing one hundred feet from the perimeter fence and embarking on a “forceful series of vegetation control.” Several dozen airmen’s sworn statements, as well as Air Force and other governmental agency reports, demonstrate consistent use of herbicides in which the Air Force used local apparatus to defoliate.

The use of herbicides on Nakhom Phanom (NKP) was noted in the 1973 CHECO report and in an airman’s sworn statement. Many other documents demonstrate that herbicides were widely used throughout Southeast Asia. The article “Viet Cong—Right or Wrong,” published in the National Guardsman in 1966, notes that the Defense Department’s Advance Research Project Agency was moving forward with defoliant improvement projects in Thailand. This implies that defoliant enhancement projects occurred after the initial herbicide testing in 1964-65. Again, this supports veterans’ statements regarding the use of herbicides to clear bases in Thailand during this period.

The author of a 1982 article published in the Journal of Legal Medicine, titled “Agent Orange: Government Responsibility for Military Use of Phenoxy Herbicides,” asserted that “every American who served in Southeast Asia was potentially exposed to Agent Orange, as the herbicide was used to clear areas before construction and to defoliate compounds, LZs, and FSBs.”

For confirmation, the author cites an annotation to the 1979 committee hearings on Senate Bills 741 and 196. During those hearings, Congress considered perimeter spraying. As was the case with the Air Force unit histories in Thailand, the 1979 hearing noted that herbicides were widely applied on bases to maintain security.

Ranch Hand herbicide spray missions were not prohibited in Thailand. In November 1969 the NKP Commander requested Ranch Hand help to defoliate the ordnance impact area. In his request, the Commander wrote: “Application must be by air because area is overgrown, and ground spraying would be extremely dangerous because of live munitions in the area.”

To create a standard requirement for the use of herbicides, the USAF established annual training and standard operating procedures. The training took place on Takhli in March 1969 and July 1970, with enlisted personnel from all Thailand bases. The 355th Civil Engineer Squadron and the Pacific Air Force (PACAF) Command Agronomist supported the training. This training indicates that the Air Force leadership took a consistent approach regarding the application of herbicides on Thailand bases.

The purpose of the training was to “train and certify Thailand-based personnel who will be supervising herbicides for vegetation control” and “train other personnel on the use, application, dangers, and cautious handling of herbicides.” Each class consisted of twelve NCOs. The program sponsors said that some personnel would receive “their own copy of the herbicide manual.” Although the whereabouts of the manuals is unknown, its publication clearly shows that there was repeated use of herbicides throughout Thailand. Since Raymond Gross, a PACAF agronomist, conducted the training, the herbicide manual probably also was used elsewhere in Southeast Asia.

This view is reinforced by the fact that civil engineers developed a standard operating procedure for the disposal of herbicides due to concerns that haphazard handling could be a source of pollution. Although the SOP is not available or remains classified, its development and enforcement highlights the prevalence of herbicide use and the concerns about misuse on bases throughout Thailand.

Photo by SP6 Eugene M. Randon


Current VA policy establishes that “special consideration of herbicide exposure on a factual basis should extend to Veterans whose duties placed them on or near the perimeters of Thailand military bases.” So, without evidence of direct exposure to herbicides, Thailand veterans must demonstrate that their duties placed them near the perimeter of bases where herbicides were used.

This requirement is arbitrary and unwarranted considering the widespread use of herbicides in Thailand. Veterans who served in Thailand were exposed to the same herbicides as were veterans who served in Vietnam, and in much the same way. VA should establish the same presumption of exposure for Thailand veterans that in-country Vietnam veterans were afforded under Public Law 102-4.

An especially interesting book documenting the Air Force’s involvement in the war in Southeast Asia was written by Maj. William A. Buckingham, Jr., of the Office of Air Force History. He accurately emphasizes that the Air Force served as a mechanism of national policy in conducting herbicide spraying. The book is a classic review of the way in which military policy—including the widespread, indiscriminate use of herbicides—was made in the Vietnam and Thailand. Once again, attention is drawn to Southeast Asia, as opposed to just Vietnam. In August of 1962, the report said, the Defense Department considered herbicide spraying for crops in Phu Yen Province to deny the enemy food sources.


The first uses of defoliants in Thailand did not begin with Ranch Hand operations. According to the first of ten reports prepared for the National Academy of Sciences by the Institute of Medicine in 1994 titled “Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam,” the earliest recorded use of defoliants involving the U.S. was the testing of Agent Pink in a 1953-65 limited spraying itinerary in Thailand.

The report discusses additional testing conducted in Thailand in 1964-65 to evaluate the effectiveness of aerial applications of 2,4-D and 2,4,5-T (the combined herbicides that constitute Agent Orange, which—as a byproduct—generates TCDD dioxin, the most lethal of all dioxins) and other herbicides in the defoliation of the jungle vegetation found throughout Southeast Asia. That first 1994 IOM report extensively referenced Maj. Buckingham’s book.

The National Academy of Sciences and the Office of Air Force History, in two unrelated historical studies, established that testing of defoliants in Thailand was conducted from 1953-65. There can be no doubt that defoliants used in Vietnam also were used in Thailand. While neither report reveals specific testing locations, we know that if the U.S. military is going to test in a foreign country materials that it intends to use on the enemy, the testing is going to be done in areas controlled exclusively by military personnel.

With the build-up of U.S. operations on Thailand’s military installations in 1961, it stands to reason that the testing of herbicides was conducted on and around those military areas. The herbicide’s value could be determined in similar surroundings and under American control. Also, the perimeters of sensitive military bases used by the U.S. for tactical operations could be brought up to American security standards by removing tropical growth, thereby easily allowing security forces to see the enemy.

The Pentagon has for the last forty-five years denied that Agent Orange was used in Thailand. But it also denied its use in Korea until it had to admit in November 2004 that it had been used there—after the story went public. Only then did the Pentagon admit that American troops in Korea were exposed to Agent Orange.

Consequently, the VA now recognizes certain units stationed in specific areas in the Republic of South Korea during a very limited span of time. In this light, the credibility of the Department of Defense’s repeated denials must be thoroughly questioned, particularly considering the evidence and large number of veterans who remember their bases being defoliated and who have provided sworn statements to that effect.

The documentation and testimonies—along with the willingness of veterans to testify to what they saw—and the records available in the Armed Forces Institute of Pathology, should provide more than enough evidence about what Americans and our allies were exposed to in Thailand.   

Those who served in Thailand were subjected to repeated sapper attacks, sniper fire, and perimeter penetrations. And they were repeatedly exposed to defoliants. American casualties, including loss of life, occurred through the entire duration of the U.S. presence in Thailand and Vietnam. Those who served in Thailand earned both the Vietnam Service Medal and the Vietnam Campaign Medal. Yet the families of those who lost their lives while serving in Thailand have never seen recognition by this nation for the sacrifices of their loved ones. Their names are not included on the Vietnam Veterans Memorial in Washington, D.C.

Executive Order No. 11216, signed by President Johnson on April 24, 1965, designated Vietnam and its adjacent coastal waters in or over which U.S. forces operated as a combat zone. As the war intensified, the combat zone expanded to include Laos and Cambodia. But Thailand was never included, even though hostilities spilled across its borders as the enemy attacked U.S. bases, personnel, and property. The Executive Order established an unfortunate situation in which those who served in Thailand were not officially part of the war, and this attitude has followed those veterans to this day.

Veterans who served in Thailand and have the same medical complications from chemical exposure as their brother-veterans who were in Vietnam have been denied compensation. The VA response to their claims has consistently been: “You did not serve in Vietnam; therefore, you were not exposed and are not eligible.”

For many Thailand veterans, proving presumption means having to prove boots on the ground in Vietnam, no matter how briefly. Because of record retention dates, copies of orders, travel vouchers, and pay records were purged long ago. It appears that the Pentagon and the VA waited until most records had been destroyed (or remain classified) to prevent service-connected awards and provide reasons for the denial of claims by veterans.

Despite a huge body of documentary evidence, DoD and VA maintain that Ranch Hand aircraft and herbicides were either only temporarily staged—or never staged—on Thai bases. Despite the monumental evidence presented by veteran activists, Congress has only recently moved to recognize the presumptive exposure of those who served in Thailand.

While the VA has been a favorite whipping boy of this writer for more than forty-five years, it has become obvious that VA policies are built around what little the Pentagon and other government bodies have shared. The VA has been further hamstrung by what Congress has allowed it to do or constrained it from implementing. The February 1991 Agent Orange Act (P.L.102-4) limited presumptive exposures to in-country Vietnam veterans. Neither the Department of Defense nor a multitude of government agencies has been forthright with Congress or with veterans about this decades-long inaction and entrenched secrecy.

I would be remiss if I did not recognize and thank several fellow veterans for their assistance during the research on and the preparation of the Thailand portion this article. A good deal of what is presented here is due to the unstinting sharing of their own research by brother-veterans Kurt Priessman in Texas, Charles Kelley in Georgia, Dennis Peterson in California, Dave McTavish in Pennsylvania, Dennis Zenz in North Carolina, along with Dr. Wayne Dwernychuk, formerly of Hatfield Associates, and several dozen other veterans who provided statements about their exposures in Thailand.


Unfortunately, little is known about exposures in Laos and Cambodia, and virtually no scientific data exist. In 1999 the U.S. government began to release previously undisclosed herbicide spraying records to the government of the Laos People’s Democratic Republic. According to these DoD records, untold millions of gallons of Agent Orange and other dioxin-contaminated herbicides were sprayed on Laos between 1964-73. That disclosure represents the only official and public account of secret herbicide spraying activities in Laos.

The CIA and covert military units conducted an air war in Laos beyond the scope of the world’s media. That war was never fully sanctioned or approved by Congress. To this day, a concise understanding of this secret warfare has not been presented to a broad international public. Because of the lack of records and academic and scientific research, postwar actions regarding the use of Agent Orange in Laos and in Vietnam differ significantly.

Herbicide spraying records are incomplete and have been only partially disclosed. Public health and environmental surveys on dioxin levels in soil, milk, blood, and fat tissues are nonexistent, except for a small private sampling in Sepone in 2001 performed by Dr. Arnold Schecter of the University of Texas, Dallas. Congressional funding and U.S. military assistance for other postwar problems are inextricably linked to the POW/MIA question.

The tragedy does not end there. Along the southern spine of Laotian mountains ran the Ho Chi Minh Trail. As in Vietnam, the area was extensively and regularly sprayed with herbicides over several years, but few outsiders know about it. The consequences of the herbicide spraying there remain uninvestigated and unaddressed to this day. 

Since the end of the Vietnam War in 1975, there has been no comprehensive accounting, mapping, or analysis of the herbicide spraying in Laos. Neither has there been any organized or repetitive monitoring of the sprayed zones for dioxin-related public health and ecosystem problems.

In June 2001 the Lao Ministry of Health collaborated with a team of private Americans on the first dioxin survey in the country. The Laotian Vice-Minister of Health approved a brief exploratory mission to Sepone in Savannakhet Province for Dr. Schecter, a leading dioxin specialist, along with Roger Rumpf and Dr. Hansila Praphouseuth of the Ministry of Health. They collected samples of blood, mothers’ milk, soil, and fatty tissues of animals, which Dr. Schecter had analyzed.

A Laos Agent Orange Survey was conceived and proposed by a group of Americans and Lao officials in the spring of 2002 during the Joint Viet-Nam-U.S. Scientific Conference on Human Health and Environmental Effects of Agent Orange/Dioxin. Congress had, earlier that year, included Laos in its authorization for continuation of Agent Orange/dioxin research and assistance. The National Institute for Environmental Health Studies of the National Institutes of Health administers the funds. 

Photo by SP5 Thomas L.


The Fund for Reconciliation and Development (FRD) working in these two nations published a summary on the use of Agent Orange and other herbicides in Laos and Cambodia during the Indochina War. As most of the records of herbicide spraying remain classified and inaccessible, FRD has attempted to collect what is known and to identify gaps for future research. The following are preliminary findings from declassified U.S. military and State Department documents held at the National Archives and Records Administration in College Park, Maryland, as well as from some secondary sources.

The 1962 Geneva Accords proclaimed Laos a neutral country and forbade outside military involvement there. As the war in Vietnam escalated, however, neither the U.S. nor North Vietnam was able to resist intervening. As local Lao revolutionaries and their North Vietnamese allies built a network of paths along the border—the Ho Chi Minh Trail—covert U.S. operations tried to stop them. Among the methods was defoliation by herbicides, primarily Agent Orange. 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. The environmental and human consequences never entered the calculation; nor, with few exceptions, did the international legality of spraying seem to trouble American leaders.

By far the greater concern was preservation of secrecy, in case evidence of chemical use might be turned into communist propaganda. The primary tactic in the “secret war,” however, was bombing, which caused immense damage in almost every province of Laos. The use of herbicides, a sideshow to a sideshow, was reported during the conflict but officially denied until 1982, when Air Force historian Maj. 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 U.S. Ambassador William Sullivan said that “secret” was not the right word to describe the herbicide program: “Rather, it was not admitted or confirmed.”

According to Buckingham, the Air Force conducted herbicide operations in Laos from December 1965 to September 1969. Former Chief Air Force Historian Richard Kohn claims that this spraying took place “with the permission of the Laotian government” headed by President Souvanna Phouma. But archival documents make it clear that Amb. Sullivan and other officials provided very little information to the Lao, who may have preferred to remain uninformed about the details of covert U.S. operations in their country.

The “experimental” use of herbicides outside of South Vietnam was first considered by the Department of Defense as early as October 1962 to “clear off jungle access routes” in a broad, undefined area around “the Cambodian-Laotian-North Vietnam border”—a difficult task given that Cambodia and North Vietnam have no common border, with several southern Laotian provinces in between. This plan was never implemented in full, but it gives a sense of what was to follow. Sullivan expressed nervous opposition at first, citing “allegations concerning earlier [U.S.] uses of chemical weapons in Laos.”

Exactly what those allegations were is unclear, but they may 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 eliminated Sullivan’s concerns about the program. He 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, just before the Air Force spraying program was to begin, Sullivan wrote a memo to Washington. “I am convinced that our efforts in Laos, particularly along infiltration routes, are critical to U.S. forces engaged in South Vietnam,” he said. “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 articles in American news media broke in December 1965. In February 1966 the Washington Post and New York Times ran front-page articles on defoliation operations in Laos. 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.” In response to a November 1969 congressional query, MACV reported 434 sorties in Laos beginning in December 1965 and ending in September 1969.

Air Force spraying was heaviest during the first half of 1966, with more than two hundred sorties spraying approximately 200,000 gallons of Agent Orange. Spraying continued at a relatively rapid rate until February 1967, when apart from 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. These totals, from a classified Air Force study, are around 20 percent higher than what MACV reported to Congress.

Agent Orange was the primary herbicide used (about 75 percent), followed by Agents Blue (15 percent) and White (10 percent). 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 likely are scattered in military archives.

The limited number of maps and coordinates found at the National Archives suggests that the greatest concentration of spraying occurred both north and south of the Demilitarized Zone near the Vietnamese border in Savannakhet and Attapeu provinces. Declassified documents record the aircraft used for Air Force operations: mostly UC-123Ks 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 and from ships in the South China Sea.

A January 1969 memo from the Chemical Operations Division at MACV headquarters in Saigon noted that “the legality of these out-of-country operations is uncertain,” and cited increasing risks from ground fire near the DMZ. 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.

Herbicides also were used in Laos to destroy enemy crops. Citing effective use in South Vietnam, Gen. Westmoreland first proposed crop destruction in Laos in May 1966. Records from the U.S. Embassy in Vientiane list sixty-four crop destruction missions from September 1966 to September 1969 targeting 20,485 acres. Agent Blue was the most frequently used chemical. After the Lao government banned opium cultivation in 1971, herbicides were used to destroy hill tribe poppy crops as late as 1974.

All this data refers only to spraying carried out by the U.S. Air Force using fixed-wing aircraft. It may not be a complete record even of these operations, although the start and end dates can be confirmed by multiple sources in declassified records. What is not included is spraying conducted by helicopter and directly on the ground. The Air Force and other units had this capability. Also unconfirmed is herbicide use by Air America or the CIA, whose records are still classified. The 1971-73 opium destruction missions were probably carried out on this basis, and secondary sources report that the CIA also had spray capability, possibly operating out of Thailand.

In contrast to the covert spraying in Laos over a long period, one incident of herbicide use in Cambodia resulted in a major international incident. This attack took place on French and Cambodian-owned rubber plantations in Kompong Cham province in April and May 1969, at a time when the U.S. had no diplomatic relations with the government of Prince Norodom Sihanouk. Following official complaints from the Cambodians to the U.S. through Australian intermediaries, the State Department agreed to send a team of experts to investigate the damage, hoping that the story would go away.

Memos and telegrams from the period appear confused about who did the spraying and what if any responsibility the U.S. should take for the incident. Initial theories ranged from drift from spraying in neighboring Tay Ninh province in Vietnam, to an elaborate Viet Cong provocation. No one outside of the embassies appeared to believe these ideas. The State Department inspection team, comprised of Drs. C.E. Minarik, Fred Tschirley, and two others, confirmed the extent of the damage to 173,000 acres (7 percent of Kompong Cham province), 24,700 of them seriously affected. The rubber plantations added up to about a third of Cambodia’s cultivated acreage and represented a loss of 12 percent of the country’s export earnings. Defoliation probably took place at a higher than normal altitude and occurred at night, which made spraying less accurate and prevented crews from monitoring their spray racks.

Minarik and Tschirley were under strict orders not to divulge their findings, however. They also were warned not to look at evidence of “alleged U.S.-caused damage outside these terms of reference.” They cited evidence of CIA-sponsored spray capability and suggested that helicopters may have been used. Available documentation tends to support this hypothesis. William Sullivan, promoted to Undersecretary of State for East Asian and Pacific Affairs in Washington, confirmed in November 1969 that “the rubber plantations were not defoliated inadvertently,” but the idea that it was an enemy provocation “has some problems.”

In addition to the Kompong Cham attack, what additional incidents of herbicide use took place in Cambodia? There is no documentary evidence to suggest that spraying of any kind took place before 1969. The only covert American operation from 1967-69, Operation Daniel Boone, involved Special Forces and Montagnard reconnaissance teams on the ground in Rattanakiri and Mondulkiri provinces—not an operation likely supported by aerial spraying.

A February 23, 1970, telegram from the U.S. Embassy in Saigon, titled “Cambodian Complaints of Herbicide Damage,” states: “There were no, repeat no, UC-123K herbicide missions opposite Mondulkiri on December 18. Missions were flown opposite Mondulkiri on other dates in December, including December 17 and 19. Past experience shows [Cambodian] protests are not always accurate.”

Because of the Kompong Cham incident and similar pressures from the South Vietnamese government, restrictions began to be placed on herbicide use in 1970. In March 1971 Secretary of Defense Melvin Laird requested that he personally approve any herbicide operations in Laos, Cambodia, or Thailand. The scope of such additional spraying remains unclear, but probably did not occur.

These findings are clearly only a partial record of herbicide use in Laos and Cambodia. Many additional sources remain to be examined, many of them classified. Among these are all CIA records.

The full extent of American use of herbicides in these covert actions will require much more research both in the U.S. and on site. In today’s atmosphere of security concerns over terrorism and increasing government secrecy, even previously declassified records are now being re-classified and screened by the National Archives and other government repositories. This includes, for instance, the Project CHECO reports on which Buckingham based much of his data.

It is ironic that the U.S. Government goes out of its way to avoid referring to Agent Orange as a “chemical weapon” for public relations and liability reasons, except when a researcher attempts to gain access to sensitive records. In these cases, researchers are denied access to chemical subject matter that, according to a National Archives notice, “might aid terrorists or their supporters.”

Photo by SP6 Eugene M. Randon





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