Between 1949 and 1952, Operation Cumulus was an attempt by the British government to learn to control the weather via cloud seeding, primarily for future military advantage. However, on August 16, 1952, a severe flood in the town of Lynmouth occurred after nine inches of rain fell in 24 hours. Infrastructure was damaged and 34 lives were lost. Although no evidence was found that Project Cumulus was to blame, the project was abandoned after the event.
From March 1967 to July 1972, Operation Popeye involved cloud seeding by the U.S. military in an attempt to extend the monsoon season over North Vietnam and Laos, specifically over the Ho Chi Minh Trail, which was used to funnel North Vietnamese soldiers and supplies to South Vietnam. The targeted areas reportedly saw a longer monsoon season by 30 to 45 days.
But all weather modification for warfare purposes was ordered to cease. In 1977, the United Nations banned all military or hostile use of environmental modification techniques.