Forty years ago, on 31 January and 1 February 1968, Vietcong and North Vietnamese forces launched the Tet (Lunar New Year) offensive in cities and towns across South Vietnam. It was the first, and most dramatic, part of a three phase campaign. Fierce fighting raged in most of the provincial capitals as well as the national capital Saigon during early February.

The onslaught was intended to break the stalemate in the Vietnam war and stymie the mounting pressure from American forces by bringing about a “general uprising” in the South that would topple the Saigon government or at least result in negotiations to end the war on terms favourable to Hanoi.

But the offensive was repelled with heavy losses for the communists. They could not take any important town, except parts of Hue from which they were later ousted. The Vietcong in particular suffered such grievous losses that the war in the South was henceforth waged mainly by the North Vietnamese. The communist leaders had underestimated the mobility of American forces and misread the mood of the people. The general uprising they expected failed to materialize.

Yet the Tet offensive brought the communists success thousands of miles away from the battlefield, in Washington. Evidence from communist documents and post-war interviews with North Vietnamese commanders suggest that Tet's big impact on US domestic opinion was unexpected. Of course, when it did occur, Hanoi capitalized on it.

The offensive came as a shock to the American public because it had been led to believe that the war was being won and the communist side was progressively weakening. The American commanders had not understood the nature of the enemy they were pitted against and had underestimated his capabilities.

The anti-war movement already had significant traction among young Americans before Tet occurred. Now it received a big boost. Diverse interest groups joined forces with college students and pacifists to oppose the war. Most of the media too turned against it. Indeed this was the first “television war” in which stark images of battlefield scenes invaded American homes via TV cameras.