Eminent British Military HistorianJohn Keegan reminds us why Iraq is nothing like Vietnam, militrily speaking, and why the present situation is nothing like the Tet offensive. He thinks the President was unwise to be drawn into admitting that some people would see a comparison, since the media are going to play up this message and it was also the media that insisted that the Vietnam war was also lost by nightly pummeling home that message, despite the facts.
By January 1968, total American casualties in Vietnam — killed, wounded and missing — had reached 80,000 and climbing. Eventually deaths in combat and from other causes would exceed 50,000, of which 36,000 were killed in action. Casualties in Iraq are nowhere near those figures. In a bad week in Vietnam, the US could suffer 2,000 casualties. Since 2003, American forces in Iraq have never suffered as many as 500 casualties a month. The number of casualties inflicted in Iraq are not established, but are under 50,000. In any year of the Vietnam war, the communist party of North Vietnam sent 200,000 young men to the battlefields in the south, most of whom did not return. Vietnam was one of the largest and costliest wars in history. The insurgency in Iraq resembles one of the colonial disturbances of imperial history....
..The recent upsurge of violence in Iraq in no way resembles the Tet offensive. At Tet, the Vietnamese new year, the North Vietnamese People's Army simultaneously attacked 40 cities and towns in South Vietnam, using 84,000 troops. Of those, the communists lost 45,000 killed. No such losses have been recorded in Iraq at any place or any time. The Tet offensive proved to be a military disaster for the Vietnamese communists. It left them scarcely able to keep up their long-running, low-level war against the South Vietnamese government and the American army.
Indeed, insofar as Tet was a defeat for the United States and for the South Vietnamese government, it was because the American media decided to represent it as such. It has become a cliché to say that Vietnam was a media war, but so it was. Much of the world media were hostile to American involvement from the start, particularly in France, which had fought and lost its own Vietnam war in 1946-54. The defeat of Dien Bien Phu rankled with the French and there were few who wanted to see the Americans win where they had failed.
See John Keegan's many tomes on miltary history listed here.