Operation Popeye

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Operation Popeye (Project Controlled Weather Popeye / Motorpool / Intermediary-Compatriot) was a military cloud-seeding project carried out by the U.S. Air Force during the Vietnam War in 1967–1972. The highly classified program attempted to extend the monsoon season over specific areas of the Ho Chi Minh Trail, in order to disrupt North Vietnamese military supplies by softening road surfaces and causing landslides.

The former U.S. Secretary of Defense, Robert S. McNamara, was aware that there might be objections raised by the international scientific community but said in a memo to the president that such objections had not in the past been a basis for prevention of military activities considered to be in the interests of U.S. national security.

The chemical weather modification program was conducted from Thailand over Cambodia, Laos, and Vietnam and allegedly sponsored by Secretary of State Henry Kissinger and the CIA without the authorization of then Secretary of Defense Melvin Laird, who had categorically denied to Congress that a program for modification of the weather for use as a tactical weapon even existed.[1]

Build up[edit]

A report titled Rainmaking in SEASIA outlines use of lead iodide and silver iodide deployed by aircraft in a program that was developed in California at Naval Air Weapons Station China Lake and tested in Okinawa, Guam, the Philippines, Texas, and Florida in a hurricane study program called Project Stormfury.[2][3]

Project Popeye was the experiment in increased rainfall through cloud seeding leading up to Operation Popeye. The technical aspects of the experiment were verified by Dr. Donald F. Hornig, Special Assistant to the President of the United States for Science and Technology. During October 1966, Project Popeye was tested in a strip of the Laos panhandle east of the Bolovens Plateau in the Se Kong River valley. The government of Laos was not informed of the project, its methods, or its goals. The test was conducted by personnel from the Naval Ordnance Test Station located at China Lake California. The results of this specific experiment are unknown, but other less surreptitious cloud seeding tests have been conducted.[citation needed]


Operation Popeye's goal was to increase rainfall in carefully selected areas to deny the Vietnamese enemy, namely military supply trucks, the use of roads by:[4]

  1. Softening road surfaces
  2. Causing landslides along roadways
  3. Washing out river crossings
  4. Maintaining saturated soil conditions beyond the normal time span.

The goal of the operation was to extend days of rainfall by about 30 to 45 days each monsoon season.[5]


The 54th Weather Reconnaissance Squadron carried out the operation using the slogan "make mud, not war."[6] Starting on March 20, 1967, and continuing through every rainy season (March to November) in Southeast Asia until 1972, operational cloud seeding missions were flown. Three C-130 Hercules aircraft and two F-4C Phantom aircraft based at Udon Thani Royal Thai Air Force Base in Thailand flew two sorties per day. The aircraft were officially on weather reconnaissance missions and the aircraft crews as part of their normal duty also generated weather report data. The crews, all from the 54th Weather Reconnaissance Squadron, were rotated into the operation on a regular basis from Guam. Inside the squadron, the rainmaking operations were code-named "Motorpool".[7]

The initial area of operations was the eastern half of the Laotian panhandle. On 11 July 1967, the operational area was increased northward to around the area of the 20th parallel and included portions of far western North Vietnam. In September 1967, the A Shau Valley in South Vietnam was added to the operational area. Operations over North Vietnam were eliminated on April 1, 1968, concurrent with conventional bombing restrictions being put into effect. The southern region of North Vietnam was added to the operational area on September 25, 1968, and then removed on November 1 of that year concurrent with a halt to conventional bombing of North Vietnam. In 1972, most of northeastern Cambodia was added to the operational area.[citation needed]

All rainmaking operations ceased on July 5, 1972.[citation needed]

Public revelation[edit]

Reporter Jack Anderson published a story in March 1971 concerning Operation Popeye (though in his column, it was called Intermediary-Compatriot). The name Operation Popeye (Pop Eye) entered the public space through a brief mention in the Pentagon Papers[8] and a July 3, 1972, article in the New York Times.[9] Operations in Laos ceased two days after the publication of the Times article.[citation needed]

The press stories led to demands from members of the U.S. Congress, led by Senator Claiborne Pell, for more information. U.S. House and Senate resolutions in favor of banning environmental warfare were passed as Senate Resolution 71 on July 11, 1973, H.R. 116 of 1974, H.R. 329 of 1974 and H.R. 28 of 1975.[citation needed]

Current legal status[edit]

Weather modification procedures, when performed to achieve a military end, now fall under the provenance of the Environmental Modification Convention.

See also[edit]


  • Weather Modification Hearing, United States Senate Subcommittee on Oceans and International Environment of the Committee on Foreign Relations, March 20, 1974

Published government documents[edit]

  • Keefer, Edward C. Foreign Relations of the United States 1964-1968 Volume XXVII Laos United States Government Printing Office, 1998.


  1. ^ "Rainmaking used as a Weapon in SE Asia". Daytona Beach Morning Journal. Daytona Beach, Florida. The New York Times News Service. 19 May 1974.
  2. ^ SEASIA Rainmaking (Report). Department of Defense. 1974. Archived from the original on 12 June 2009.
  3. ^ Project Stormfury (PDF) (Report). United States Department of the Navy. May 1971. Archived from the original (PDF) on February 1, 2014.
  4. ^ "ENMOD and the US Congress". Sunshine-project.org. Archived from the original on 27 August 2009. Retrieved 25 July 2009.
  5. ^ The Encyclopedia of the Vietnam War A Political, Social, and Military History. ABC-CLIO. 2011. p. 921.
  6. ^ Thomas, Will. "Weather Warfare/Global Dominance Over Weather/Full Spectrum Dominance By Us Over Weather". Willthomas.net. Archived from the original on 23 February 2007. Retrieved 25 July 2009.
  8. ^ "The Pentagon Papers, Gravel Edition, Volume 4, Chapter 2, "US Ground Strategy and Force Deployments, 1965-1968, pp. 277-604, 3rd section". Mtholyoke.edu. Archived from the original on 2009-06-12. Retrieved 2009-07-25.
  9. ^ Seymour M. Hersh (July 3, 1972). "Rainmaking Is Used As Weapon by U.S.; Cloud-Seeding in Indochina Is Said to Be Aimed at Hindering Troop Movements and Suppressing Antiaircraft Fire Rainmaking Used for Military Purposes by the U.S. in Indochina Since '63". New York Times. Retrieved 2009-07-25.

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