Operation Popeye

Operation Popeye (Project Popeye/Motorpool/Intermediary-Compatriot) was a US military cloud seeding operation (running from March 20, 1967 until July 5, 1972) during the Vietnam war to extend the monsoon season over Laos, specifically areas of the Ho Chi Minh Trail. The operation seeded clouds with silver iodide, resulting in the targeted areas seeing an extension of the monsoon period an average of 30 to 45 days.

As the continuous rainfall slowed down the truck traffic, it was considered relatively successful.Project Popeye was an experiment in increased rainfall through cloud seeding jointly approved by the U.S. Department of State and U.S. Department of Defense. 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.

The government of Laos was not informed of the project, its methods or its goals.Robert S. McNamara, U.S. Secretary of Defense, 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.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 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.