13 February 1965 – President Lyndon B. Johnson expanded American air operations in August 1964, when he authorized retaliatory air strikes against North Vietnam following a reported attack on U.S. warships in the Gulf of Tonkin.
Later that year, Johnson approved limited bombing raids on the Ho Chi Minh Trail, a network of pathways that connected North Vietnam and South Vietnam by way of neighboring Laos and Cambodia. The president’s goal was to disrupt the flow of manpower and supplies from North Vietnam to its Viet Cong allies.
On 15 February 1965, the President authorized Operation Rolling Thunder, an American bombing campaign.
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.
From 1965 to 1968, about 643,000 tons of bombs were dropped on North Vietnam, and 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. (2)
Source: (1) https://www.history.com/topics/vietnam-war/operation-rolling-thunder; (2) History.com; gif from Wikipedia