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While almost all of the 20 million gallons of herbicides were sprayed in southern Vietnam, the U.S. war effort (and herbicide spraying) spilled over into avowedly neutral Laos. Little is known about the present-day consequences of the spraying there.

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A Brief History of U.S. Spraying in Laos

Flight records taken from the HERBS database show that 209 missions between 1965 and 1970, sprayed a total of at least 537,495 gallons of tactical herbicides. The heaviest spraying began in early 1966 and continued at a steady rate until February 1967, after which the rate of spraying became intermittent until October 1970. For over five years, these spray runs were coordinated out of Bien Hoa air base, with some also out of Ton San Nhat and Da Nang, in Vietnam. Spraying in Laos was also conducted for a period of time out of bases in Thailand. 

The Ho Chi Minh Trail had extended into Lao territory, from Vietnam, which included Lao provinces bordering Vietnam, such as Savannakhet, Salavan, Sekong and Attapeu provinces, all abutting Vietnam’s southwestern border. These Lao southeastern provinces were heavily sprayed, as the U.S. tried to destroy the Ho Chi Minh Trail. Khammouane province, to the north of Savannakhet, and Champasak province, bordering Cambodia, were also sprayed, but comparatively less so.

As in Vietnam, the herbicides were used not only to defoliate forests, but also to destroy crops. Records from Military Assistance Command Vietnam (MACV) show that 64 crop destruction missions (an area a total of 32 square miles along the Ho Chi Minh Trail) took place between September 1966 and September 1969. The spraying and heavy bombing forced villagers to flee to the hills for up to ten years. The food supply chain was inevitably upended as a result, triggering an immense loss of crops and livestock that was followed by malnutrition lasting for decades after the war.

​According to William Buckingham’s history of Operation Ranch Hand, the U.S. Air Force sprayed 419,850 gallons—of which, 75 percent were Agent Orange, 15 percent Agent Blue, and 10 percent Agent White—over 255 square miles of Laos, up until September 1969. Ranch Hand records show that the total was closer to 600,000 gallons. 

​Like the bombing of Laos during the war, the use of herbicides in Laos was secretive until 1982, when a draft of Buckingham’s study of Operation Ranch Hand was made public. Much about the U.S. war effort in Laos still remains classified.

Very little is known about spraying that may have been done under the auspices of the U.S. Central Intelligence Agency (CIA); nor do we know if there was any hand or helicopter spraying done on bases controlled by the U.S. or allied forces. For a very short time in 1968, Air America used one of its Porter aircraft to spray Agent Orange in central Laos out of Long Tieng. Technical issues with the spray nozzles made this impractical, however.

In 2019, the U.S. Department of Defense released a list of where herbicides were used outside of Vietnam. It states that Agent Orange was stored and loaded onto planes at Udorn air base in Thailand between October 1968 and September 1969 and used for “missions flown in northern Laos.” Only three spraying missions, which were conducted in September 1969 over an area approximately 60 miles northeast of the Lao capital of Vientiane, show up in the HERBS database—very much a vast understatement of the true magnitude of the U.S. herbicide spraying campaigns.

While there is no complete account of the use of herbicides in Laos, War Legacies Project began a survey in 2014 to determine the impact of aerial herbicide spraying in Laos and is working toward capturing the full picture.

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