By Paul Reynolds
World Affairs correspondent, BBC News website
President Bush's new plan for Iraq - with its reinforcements of 20,000 US troops - has echoes of Vietnam in the belief that another push will get the job done.
The White House believes sending more troops may be the answer
The strategy also has potential contradictions between the hope for quick results and the gradualism favoured by the US Army's newly formulated counter insurgency tactics.
These were drawn up by Gen David Petraeus, soon to be the new US commander in Iraq.
The media's use of the word "surge" to describe the additional forces, implying something rapid but short-lived, also goes against the concepts developed by Gen Petraeus.
History does not repeat itself exactly, so what happened in Vietnam might not happen in Iraq, but there are parallels that are interesting to note
- First there is the realisation in Washington that it is not winning. Mr Bush has admitted this himself
- Second, there is a policy of trying to hand over responsibility to the local government in the midst of battle, not after it - this happened in Vietnam with the policy of Vietnamisation
- Third, there is the belief by the US administration that more troops are an important part of the answer
- Fourth, there is an opposite belief by others that the enterprise cannot work and that disengagement must be sought - US public doubt is a theme common to both conflicts
- Fifth, in Vietnam too the president consulted an outside group - they were called the Wise Men and, like the Iraq Study group, they too urged a policy designed to lead to withdrawal
The Bush factor
There are also major differences. Vietnam was on a much larger scale. The US deployed more than half a million troops. It was fighting against the regular North Vietnamese army as well as against the Viet Cong insurgency. It was a bigger task.
There is also the Bush factor. He is already acting against the thrust of the Iraq Study Group proposals, which were for a US withdrawal from the battle as soon as possible. Instead he appears to be throwing more troops into the battle. He is determined not to have a Second Vietnam.
If American leaders were convinced that communism would take over South Asia with the fall of South Vietnam, then George Bush is even more convinced that Islamic fundamentalism might take over with the fall of Iraq.
The memoirs of President Lyndon Johnson, The Vantage Point, make for instructive reading. They show the conflict between confidence and doubt and how the options gradually became more limited.
The key year determining the US future in Vietnam was probably 1968.
That January, the North Vietnamese army and the Viet Cong launched the Tet offensive. Although it was beaten off, Vice-President Hubert Humphrey remarked to President Johnson: "Tet really set us back."
The US commander Gen William Westmoreland asked for more troops and got them. Johnson wrote: "He believed that exploiting the opportunity 'could materially shorten the war'."
Johnson himself writes of his hopes that South Vietnam could do more for itself: "I wanted the South Vietnamese to carry a heavier share of the burden of fighting for their country."
However, underneath, he was doubtful about the future and soon afterwards, Lyndon Johnson announced his intention of not running for the presidency again.
Time to go
His memoirs remind us of the false optimism that permeated the administration at the time.
"General Creighton Abrams [deputy to Westmoreland but later to take over] gave me a full report on the tactical situation and spoke encouragingly of the improvements being made by the Vietnamese military," he wrote of 26 March 1968.
Johnson worried that the Wise Men - a group of grandees who had shaped American policy after the Second World War and from whom Johnson sought advice on Vietnam - "had been treated to a diet of pessimistic press reports on Vietnam".
Iraqi police would assume a greater role according to US plans
The Wise Men had pessimism of their own.
Johnson says that on the same day as the confident Gen Abrams reported, Dean Acheson, a former secretary of state, said "he felt that we could no longer do what we set out to do in the time available; we had to disengage". Most of the Wise Men agreed.
And so the policy of Vietnamisation emerged from 1968 onwards, accelerated by Richard Nixon who won the presidency later that year.
A history of the development of the South Vietnamese army written in 1991 by Brig-Gen James Collins, the US Army's chief of military history, pinpointed the decision:
"On 16 April  the deputy secretary of defense ordered a plan developed for gradually shifting the burden of the war to the South Vietnam forces."
After many twists and turns, the Americans did withdraw, in 1973. On 30 April 1975, North Vietnam tanks entered Saigon and the South Vietnamese were defeated.
The policy of Vietnamisation had its limits.