Operation Popeye (Project Controlled Weather Popeye / Motorpool / Intermediary-Compatriot) was a highly classifiedweather modification program in Southeast Asia during 1967–1972. The cloud seeding operation during the Vietnam War ran from March 20, 1967 until July 5, 1972 in an attempt to extend the monsoon season, specifically over areas of the Ho Chi Minh Trail. The operation was used to induce rain and extend the East Asian Monsoon season in support of U.S. government efforts related to the War in Southeast Asia.
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.
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. Fifty cloud seeding experiments were conducted with the result that 82% of the clouds produced rain within a brief period after having been seeded. It was claimed that one of the clouds drifted across the Vietnam border and dropped nine inches of rain on a US special forces camp over a four-hour period. After the successful completion of the test phase, Project Popeye transitioned from an experiment to an operational program of the U.S. Defense department.