Operation Linebacker was the codename of a U.S. Seventh Air Force and U.S. Navy Task Force 77 air interdiction campaign conducted against North Vietnam from 9 May to 23 October 1972, during the Vietnam War.
Its purpose was to halt or slow the transportation of supplies and materials for the Nguyen Hue Offensive (known in the West as the Easter Offensive), an invasion of the South Vietnam by the North Vietnamese People's Army of Vietnam (PAVN) that had been launched on 30 March. Linebacker was the first continuous bombing effort conducted against North Vietnam since the end of Operation Rolling Thunder in November 1968.
At midday on 30 March 1972, 30,000 PAVN troops, supported by regiments of tanks and artillery, rolled southward across the Demilitarized Zone (DMZ) that separated the two Vietnams. This three-division force caught the Army of the Republic of Vietnam (ARVN) and their American allies unprepared. The PAVN force struck the defensive positions of the ARVN 3rd Division and threw it into disarray. ARVN forces then fell back, and a race began between both belligerents to the bridges at Đông Hà and Cam Lộ.
By 4 April, ARVN officers had patched together a defensive line that held the PAVN at bay, but it was only a temporary respite. Although the conventional attack by the PAVN, which included the extensive use of armor and heavy artillery, riveted the attention of the allies on the northern provinces, it was only the first of three such operations that were launched that spring. On 5 April, a PAVN force of 20,000 crossed the border from their sanctuaries in Cambodia in another three-division, combined arms force to attack Bình Long Province, north of Saigon. They quickly seized the town of Lộc Ninh and then surrounded the town of An Lộc, cutting the road to the capital.
On 12 April, the PAVN struck again, this time moving in from eastern Laos and seizing a series of border outposts around Đắk Tô in Kon Tum Province in the Central Highlands. The PAVN then proceeded east toward the provincial capital of Kon Tum. Hanoi had initiated the offensive to coincide with the winter monsoon, when continuous rain and low cloud cover made air support difficult.
The initial U.S. response to the offensive was lackadaisical and confused. The Pentagon was not unduly alarmed and the U.S. Ambassador to South Vietnam and Commander, U.S. Military Assistance Command, Vietnam, General Creighton W. Abrams, were both out of the country. President Richard Nixon's first response was to consider a three-day attack by Boeing B-52 Stratofortress heavy bombers on Hanoi and the port city of Haiphong. His National Security Advisor, Dr. Henry Kissinger, convinced Nixon to reconsider, since he did not want to jeopardize the formalization of the Strategic Arms Limitation Treaty (SALT I) with the Soviet Union, that was due to be signed in May. Another stumbling block to the plan was Abrams' desire to utilize the available bombers (with their all-weather capability) to support the ARVN defense.
Nixon and Kissinger considered a plan offered by the Joint Chiefs of Staff to be both unimaginative and lacking in aggression. On 4 April, Nixon authorized the bombing of North Vietnam (which had been limited to reprisal raids just above the DMZ) up to the 18th parallel. To prevent a total ARVN collapse and to protect American prestige during the upcoming summit meeting with Soviet general secretary Leonid Brezhnev, Nixon decided to risk a massive escalation of force.
Due to the continuous withdrawal of American forces as part of the policy of Vietnamization, at the time of the invasion fewer than 10,000 U.S. combat troops remained in South Vietnam, and most of them were scheduled to leave within the next six months. The number of combat aircraft stationed in Southeast Asia was less than half that of its peak strength in 1968–1969. At the beginning of 1972, the U.S. Air Force (USAF) had only three squadrons of McDonnell Douglas F-4 Phantom II fighter-bombers and one squadron of Cessna A-37 Dragonfly light attack aircraft, a total of 76 aircraft, stationed in South Vietnam. Another 114 fighter-bombers were located at bases in Thailand. 83 B-52s were stationed at U-Tapao RTAFB, Thailand and at Andersen Air Force Base, Guam. The U.S. Navy (USN)'s Task Force 77 (stationed in the Gulf of Tonkin), had four aircraft carriers assigned to it, but only two were available at any one time to conduct operations. Their air wings had approximately 140 aircraft.
American and Republic of Vietnam Air Force (RVNAF) aircraft had been supporting the defense (weather permitting) since the beginning of the offensive. These strikes were conducted in support of ARVN forces, and included those of the air wings of the carriers USS Coral Sea and USS Hancock. The bad weather limited the ability of the U.S. aircraft to assist in stemming the North Vietnamese onslaught. By 6 April, at naval and air bases around the globe, American forces were put on alert and ships and aircraft squadrons began moving toward Southeast Asia.
The U.S. began a rapid build-up of airpower. The USAF deployed 176 F-4s and 12 F-105 Thunderchiefs from bases in the Republic of Korea and the U.S. to Thailand between 1 April and 11 May in Operation Constant Guard. Strategic Air Command (SAC) dispatched 124 B-52s from the U.S. to Guam bringing the total B-52 strength available for operations to 209. The USN cut short its port period for the carriers USS Kitty Hawk and USS Constellation and ordered USS Midway, USS America and USS Saratoga to augment the fleet so that four or more carrier air wings could conduct missions simultaneously. 7th Fleet assets in local waters were thereby increased from 84 to 138 ships.
USAF tactical strikes against North Vietnam north of the 20th parallel were authorized on 5 April under the nickname Freedom Train. The first mass B-52 raid directed against the north was conducted on 10 April when 12 B-52s, supported by 53 attack aircraft, struck petroleum storage facilities around Vinh. By 12 April, Nixon had informed Kissinger that he had decided on a more comprehensive bombing campaign which would include strikes against both Hanoi and Haiphong.
The following day 18 B-52s struck Thanh Hóa's Bai Thuong Air Base. Three more days followed before another strike, this time by another 18 bombers in a pre-dawn attack against an oil tank farm outside Haiphong. They were followed by more than 100 tactical aircraft attacking targets around Hanoi and Haiphong during daylight. Between 6 and 15 April, U.S. aircraft also struck and destroyed the Paul Doumer and Thanh Hóa bridges and the Yên Viên railway marshalling yard. This marked the introduction of laser-guided bombs against strategic targets in North Vietnam. Both bridges had previously been attacked unsuccessfully with conventional bombs and even missiles. The B-52s were then withdrawn from operations in the north and when they returned in June, their missions would be limited to South Vietnam.
By mid-month, nearly all of North Vietnam had been cleared for bombing raids for the first time in over three years. Air Force and Navy commanders and pilots were relieved that Nixon (unlike President Johnson) left the operational planning to local commanders and loosened the targeting restrictions that had hampered Operation Rolling Thunder. Between 1 May and 30 June B-52s, fighter-bombers, and gunships had flown 18,000 sorties against formidable anti-aircraft defenses with the loss of 29 aircraft.
The U.S. also now began what North Vietnamese historians have described as "using devious political and diplomatic schemes...to cut back the amount of aid being supplied to us by socialist nations". On 20 April Kissinger met secretly with Brezhnev in Moscow. Unwilling to jeopardize the normalisation of relations with the West and wary of Washington's growing relationship with Beijing, Brezhnev agreed to apply pressure to Hanoi to end the offensive and negotiate seriously.
Brezhnev then arranged for another secret meeting between Kissinger and Hanoi's lead negotiator Le Duc Tho, to be held on 2 May in Paris. On the day, the two men met for a session that Kissinger later described as "brutal and insulting." The North Vietnamese, sensing victory, were in no mood to make concessions. As a result of this meeting and the fall of Quảng Trị City Nixon was prepared to up the ante, stating that "the bastards have never been bombed like they're going to be bombed this time".