From 1964 to 1973, the Lao People's Democratic Republic became involved in the Second Indochina War (known as the Vietnam War in the West) between the United States and North Vietnam. For those nine years, Lao PDR was subjected to the heaviest bombing in world history. U.S. bombing records indicate that there were over 580,000 bombing missions carried out and over two million metric tons (2.2 million U.S. tons) of ordnance dropped on Lao PDR during the conflict.
Journal of Conventional Weapons Destruction: Vol. 10
, Article 24.
Available at: http://commons.lib.jmu.edu/cisr-journal/vol10/iss2/24