Operation Rolling Thunder was a United States bombing campaign that was epic in its scale, in the destruction that it generated, in the human efforts wasted and in the resulting disillusionment of a generation in the wisdom of its leading statesmen and military leaders.

Reliance on Air Power to Achieve Victory

At the outset of the American bombing campaign over North Vietnam, the objective was one of strategic persuasion. The U.S. wanted to compel Hanoi to cease its support for the National Liberation Front insurgency in the South. Within the first few months, the mission shifted focus to the interdiction of the flow of North Vietnamese supplies and reinforcements to the South; a tactical mission. This shift coincided with the deployment of ground combat forces to South Vietnam in the summer of 1965.

In 1964, the U.S. Joint Chiefs of Staff believed that North Vietnam, a small nation with an industrial base only beginning to recover from its war with the French, would be reluctant to risk its own economic stability for the sake of the insurgency in the south. Civilian leaders in the Johnson Administration agreed with this assessment, although geopolitical concerns led them to disagree over the scope of the air campaign.

The military men advocated a course of action calculated to destroy North Vietnamese will and capacity to continue its support for the insurgency in the south. A list of targets including bridges, railway yards, shipping docks, army barracks and supply depots was drawn up. President Johnson withheld approval. The President and his civilian advisers feared that an air campaign over North Vietnam might cause the Chinese to send tens of thousands of troops across the border, as they had done in 1950 in Korea.

Initially, U.S. Air Force attacks were mounted from bases in South Vietnam. Over the course of Operation Rolling Thunder, four air bases in Thailand served as launch points for the majority of USAF activity. Aircraft refueled over Laos before continuing on to their targets in North Vietnam. U.S. Navy airstrikes were launched from aircraft carriers cruising off North Vietnam, with the majority of their targets situated in coastal regions.

On U.S. maps, Hanoi and Haiphong were marked by concentric disks. The red, outer disk represented a restricted zone, requiring permission from Washington. The yellow, inner disk represented a zone that was prohibited in all circumstances. The buffer zone marked by diagonal red stripes was established to prevent violations of Chinese airspace.

Rolling Thunder Gradually Evolves

When the first Rolling Thunder airstrikes were flown in early March 1965, no one thought that the bombing would last for more than a few months, and no one believed that North Vietnam could endure the bombing for more than half a year. Initially the bombing was limited to targets below the 19th parallel, north of the Vietnamese Demilitarized Zone but far south of the Chinese border.

Missions were severely limited by a requirement for approval from Washington for every target, on the timing of every attack and for the types of aircraft and ordnance to be used. The bombing campaign was rolled out in accordance with a doctrine of "gradualism", designed to ensure that China would have an opportunity to warn the Americans if a limit to their tolerance was being approached.

The campaign began with airstrikes targeting lines of communications just above the Vietnamese Demilitarized Zone. Attacks slowly crept northward towards the North Vietnamese major cities of Hanoi and Haiphong, continuing to hit lines of communication while adding petroleum, oil, and lubricants, electrical power stations and some industrial targets. It was hoped that these attacks would eliminate Hanoi's capacity to wage war. Bridges and ferries were destroyed, to degrade North Vietnamese ability to distribute supplies received from China and the Soviet Union. Other targets included radar installations, military barracks and ammunition depots.

The Lurking Threat of a Third World War

During 1965, attacks were forbidden within a 30 nautical mile radius surrounding Hanoi, and within 10 nautical miles of Haiphong, where North Vietnam's most important seaport was located. A buffer zone contiguous to the Chinese border was also declared off-limits. Most of these areas remained forbidden until late in 1967, and President Johnson withheld permission to bomb or mine the port at Haiphong throughout the duration of the campaign.

From Lyndon Johnson's presidential inauguration through the closing days of his administration, he refused advice to mine North Vietnamese seaports. It was feared that closing Haiphong could induce a strong and unpredictable Soviet reaction, ranging from a decision to increase material support for North Vietnam to direct Soviet intervention in the Vietnam War.

In support of this fear, Secretary of Defense Robert McNamara had pointed out before the Senate Armed Services Committee that mining North Vietnamese harbors would be an act of war in the legal sense.

War in the Skies of North Vietnam

With U.S. air superiority an indisputable fact, the North Vietnamese, with support from their Soviet and Chinese backers, began a steep build-up of anti-aircraft weapons. Over the course of the entire operation, 80% of U.S. aircraft losses were attributed to anti-aircraft guns, which included 85 and 100 mm radar-directed weapons. In 1964, North Vietnamese air defense assets were relatively few and primitive, consisting of 22 early warning radars, a handful of fire-control radars and about 700 anti-aircraft guns. As of the November 1, 1968 bombing halt, they had grown into an integrated air defense system comprising 400 radar systems, 8,050 anti-aircraft guns, 150 jet fighters, and 40 Soviet SA-2 Guideline surface-to-air missile sites.

The North Vietnamese Air Force had in February 1964 received 36 MiG-17 fighter aircraft as a "gift" from the Soviet Union. Mig-17s were subsonic and gun-armed — compared to U.S. supersonic jet fighters they seemed antiquated. In 1966, the Vietnam People's Air Force acquired supersonic, missile-armed MiG-21s from the Soviets, dramatically increasing the threat to U.S. aircraft. By 1967 the VPAF possessed an interceptor force of 100 aircraft. Many of those were based in Chinese airfields, putting those aircraft strictly off-limits to American aircraft.

USAF fighter pilots had superior aircraft and training, but the MiG pilots had a few home-field advantages. These included guidance from ground controllers using early warning radar and an option to wait for ideal circumstances. American aircraft were only attacked when they were laden with bombs, were low on fuel, or had been damaged. The MiGs were small and hard-to-see. Typically they only made one pass, at a high speed, then fled for the sanctuary of their own airfields, which were not bombed until mid-1967, or escaped across the border to China. Since they were always over friendly territory, damaged MiGs could be repaired and returned to action quickly.

The Bombing Proves Ineffective

Contrary to the intended effect of graduated escalation, Hanoi doubled down and obtained greatly increased assistance from the USSR and China, in the form of advisors and war materiel. Most significantly, this resulted in the immense expansion of North Vietnamese air defenses described above.

When petroleum, oil and lubricant storage areas began to be targeted in June 1965, first indications were that the effort would be effective in causing North Vietnam's war machine to literally grind to a halt. The CIA produced an estimate that 70% of their oil facilities had been destroyed. This proved to be only a short-term inconvenience, as Hanoi had dispersed the majority of its reserves across the country, often in small caches of around a hundred barrels. The resilience and endurance of the Vietnamese was proving to be their ultimate resource.

On the ground, large factories in heavily populated regions were split up and scattered into caves and small villages throughout the countryside. In the heavily bombed region just north of the Demilitarized Zone, entire villages were moved into underground tunnel complexes. When North Vietnamese transportation infrastructure became the focus of bombing raids, destroyed bridges were repaired or were substituted for with dirt fords, cross-stream ferries, and pontoon or sub-surface bridges. When overland supply routes came under attack, freight trains and truck convoys were split into smaller units which only moved at night.

In Code Warriors, Stephen Budiansky states that captured North Vietnamese signals intelligence documents revealed that plain-language U.S. Air Force voice transmissions provided a major source of advance warnings. In 80 to 90 percent of Rolling Thunder missions, the North Vietnamese were aware of the impending attack at least 30 to 45 minutes in advance.

The Manifest Failure of Rolling Thunder

On January 30, 1968, the People's Army of Vietnam and the Viet Cong launched the Tet Offensive; their largest offensive in the war thus far. Despite the aerial interdiction of North Vietnamese supply and material flows and the destruction of its military infrastructure, Communist forces still had enough supplies to support the offensive, and had retained the will to make enormous sacrifices.

Over the course of the three-year and nine-month bombing campaign, U.S. warplanes had flown some 300,000 sorties over North Vietnam and dropped more than 643,000 tons of bombs on that country. Despite the onslaught, North Vietnam had provided supplies and manpower sufficient to stalemate the efforts of 500,000 American troops. Nor did Rolling Thunder break the North Vietnamese will, prompting their leaders to seek a negotiated settlement to the conflict.

As 1968 drew to a close, Hanoi finally agreed to meet for preliminary discussions. In response, President Johnson declared that a complete bombing halt would go into effect on November 1, just prior to the presidential election. Three and a half years would pass before North Vietnam again became the target of intensive U.S. bombing.