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. The 54th Weather Reconnaissance Squadron carried out the operation to “make mud, not war.” 
The resultant rain and subsequent flooding of the nearby Song Con River is sometimes blamed for the move of POWs from the prison camp at Son Tay and therefore, the failure of Operation Ivory Coast.