Operation Barrel Roll was a covert U.S. Air Force 2nd Air Division and U.S. Navy Task Force 77, interdiction and close air support campaign conducted in the Kingdom of Laos between 14 December 1964 and 29 March 1973 concurrent with the Vietnam War. The operation resulted in 260 million bombs being dropped on Laos, making Laos "the most heavily bombed nation in history".