Earlier in the month, the president had ordered Operation Flaming Dart in response to communist attacks on U.S. installations in South Vietnam. These retaliatory raids did not have the desired effect of causing the North Vietnamese to cease support of Viet Cong forces in South Vietnam, and out of frustration, Johnson turned to a more extensive use of airpower.
Called Operation Rolling Thunder, the bombing campaign was designed to interdict North Vietnamese transportation routes in the southern part of North Vietnam and slow infiltration of personnel and supplies into South Vietnam. The first Rolling Thunder mission took place on March 2, 1965, when 100 U.S. Air Force and Republic of Vietnam Air Force (VNAF) planes struck the Xom Bang ammunition dump 100 miles southeast of Hanoi.
In July 1966, Rolling Thunder was expanded to include North Vietnamese ammunition dumps and oil storage facilities, and in the spring of 1967, it was further expanded to include power plants, factories, and airfields in the Hanoi-Haiphong area.
Operation Rolling Thunder was closely controlled by the White House and at times targets were personally selected by President Johnson. From 1965 to 1968, about 643,000 tons of bombs were dropped on North Vietnam. A total of nearly 900 U.S. aircraft were lost during Operation Rolling Thunder. The operation continued, with occasional suspensions, until President Johnson, under increasing domestic political pressure, halted it on October 31, 1968.
– History.com staff