Operation Popeye was a military cloud-seeding operation 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 StateHenry Kissinger and 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.
Build up
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, Philippines, Texas, and Florida in a hurricane study program called Project Stormfury. 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.
Objectives
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:
Softening road surfaces
Causing landslides along roadways
Washing out river crossings
Maintaining saturated soil conditions beyond the normal time span.
Implementation
The 54th Weather Reconnaissance Squadron carried out the operation using the slogan "make mud, not war." Starting on March 20, 1967, and continuing through every rainy season 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". 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. All rainmaking operations ceased on July 5, 1972.
Public revelation
Reporter Jack Anderson published a story in March 1971 concerning Operation Popeye. The name Operation Popeye entered the public space through a brief mention in the Pentagon Papers and a July 3, 1972, article in the New York Times. Operations in Laos ceased two days after the publication of the Times article. 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.
Current legal status
Weather modification procedures, when performed to achieve a military end, now fall under the provenance of the Environmental Modification Convention.
