Military intelligence officers working in Vietnam believed that without the support of the Ho Chi Minh government, the National Liberation Front would not survive. They therefore advocated the bombing of Hanoi in an attempt to persuade North Vietnam to cut off supplies to the NLF.

Curtis LeMay, the commander of the US air force, argued that by using the latest technology, North Vietnam could be blasted "back to the Stone Age." Others pointed out that "terror" raids on civilian populations during the Second World War had not proved successful and claimed that a better strategy would be to bomb selected targets such as military bases and fuel depots.

Three months after being elected president, Lyndon B. Johnson launched Operation Rolling Thunder. Unlike the single bombing raid in August 1964, this time the raids were to take place on a regular basis. The plan was to destroy the North Vietnam economy and to force her to stop helping the guerrilla fighters in the south. Bombing was also directed against territory controlled by the NLF in South Vietnam. The plan was for Operation Rolling Thunder to last for eight weeks but it lasted for the next three years. In that time, the US dropped 1 million tons of bombs on Vietnam.

The response of the NLF to 'Rolling Thunder' was to concentrate its attacks on the US air bases in South Vietnam. General Westmoreland, the person in charge of the military advisers in Vietnam, argued that his 23,000 men were unable to defend adequately the US air bases and claimed that without more soldiers, the NLF would take over control of South Vietnam.

On March 8, 3,500 US marines arrived in South Vietnam. They were the first 'official' US combat troops to be sent to the country. This dramatic escalation of the war was presented to the American public as being a short-term measure and did not cause much criticism at the time. A public opinion poll carried out that year indicated that nearly 80% of the American public supported the bombing raids and the sending of combat troops to Vietnam.

As the United States is the most advanced industrial nation in world it was able to make full use of the latest developments in technology in its war against North Vietnam. B-52 bombers, that could fly at heights that prevented them being seen or heard, dropped 8 million tons of bombs on Vietnam between 1965 and 1973. This was over three times the amount of bombs dropped throughout the whole of the Second World War and worked out at approximately 300 pounds for every man, woman and child living in Vietnam.

As well as explosive bombs the US air force dropped a considerable number of incendiary devices. The most infamous of these was napalm, a mixture of petrol and a chemical thickner which produces a tough sticky gel that attaches itself to the skin. The igniting agent, white phosphorus, continues burning for a considerable amount of time. A reported three quarters of all napalm victims in Vietnam were burned through to the muscle and bone (fifth degree burns). The pain caused by the burning is so traumatic that it often causes death.

The US also made considerable use of anti-personnel bombs. The pineapple bomb was made up of 250 metal pellets inside a small canister. Gloria Emerson, a reporter in Vietnam, witnessed their use: "An American plane could drop a thousand pineapples over an area the size of four football fields. In a single air strike two hundred and fifty thousand pellets were spewed in a horizontal pattern over the land below, hitting everything on the ground."

The United States also experimented with the use of plastic rather than metal needles and pellets in their anti-personnel bombs. The advantage of plastic was they could not be identified by X-Ray machines. Dropped on highly populated areas, anti-personnel bombs could severely disrupt the functioning of North Vietnam. It has been claimed that the major objective of the US bombing raids on North Vietnam was not to kill its 17 million population but to maim them. As was pointed out at the time, serious injury is more disruptive than death as people have to be employed to look after the injured where they only have to bury the dead.

One of the major problems of the US forces was the detection of the NLF hiding in the forests of Vietnam. In 1962, President Kennedy approved Operation Ranch Hand. This involved the spraying of chemicals from the air in an attempt to destroy the NLF hiding places. In 1969 alone, Operation Ranch Hand destroyed 1,034,300 hectares of forest. 'Agent Orange', the chemical used in this defoliation programme not only destroyed trees but caused chromosomal damage in people.

Chemicals were also sprayed on crops. Between 1962 and 1969, 688,000 agricultural acres were sprayed with a chemical called 'Agent Blue'. The aim of this exercise was to deny food to the NLF. However, research suggests that it was the civilian population who suffered most from the poor rice harvests that followed the spraying.

In economic terms, the bombing hurt the economy of the United States more than North Vietnam. By the beginning of 1968, it was estimated that $300 million of damage had been done to North Vietnam. However, in the process, 700 US aircraft, valued at $900 million had been shot down. When all factors were taken into consideration it was argued that it cost the United States "ten dollars for every dollar's worth of damage inflicted."