Twenty-five years later, in December 1992, the United States began a humanitarian intervention in Somalia that would be viewed as the most striking failure of the post-cold-war era. Then, in March 2003, American tanks charged across the dunes into Iraq, beginning, in the eyes of many Americans, the worst foreign policy debacle of the post-9/11 world. Tet, Somalia and Iraq: the three great post-World War II American defeats.
Except that, remarkably, Tet and Somalia were not defeats. They were successes perceived as failures. Such stark divergence between perception and reality is common in wartime, when people's beliefs about which side wins and which loses are often driven by psychological factors that have nothing to do with events on the battlefield. Tet and Somalia may, therefore, hold important lessons for Iraq.
The Tet offensive was an unmitigated disaster for the communists. Despite the advantages of surprise, the South Vietnamese insurgents, the Vietcong, failed to hold on to a single target in South Vietnam and suffered staggering losses. Of the 80,000 attackers, as many as half were killed in the first month alone, and the Vietcong never recovered. The United States had clearly won this round of the war.
Yet most Americans saw the Tet offensive as a failure for the United States. Approval of President Lyndon B. Johnson's handling of the war slipped to a low of 26 percent. Before Tet, 58 percent of Americans described themselves as ''hawks'' who wanted to step up American military involvement in the war, while 26 percent described themselves as ''doves'' seeking to reduce it. Two months after Tet, doves narrowly outnumbered hawks.
How did perceptions become so detached from reality? A key factor was overblown expectations. In the months before Tet, Johnson had begun a ''progress campaign'' to convince Americans that victory in Vietnam was just around the corner. Reams of statistics showed that infiltration rates were down and enemy casualties were up. And it worked. Public confidence ticked upwards. But after Johnson's bullish rhetoric, Tet looked like a disaster. The scale and surprise of the offensive sent a shock wave through the American psyche. As Johnson's former aide, Robert Koner, later recalled, ''Boom, 40 towns get attacked, and they didn't believe us anymore.''
The illusion of defeat was heightened by two powerful symbolic events. First, the communists attacked the American Embassy in Saigon. It was one of the smallest-scale actions of the Tet offensive, but it captured America's attention. The attackers had breached the pre-eminent symbol of the United States presence in South Vietnam: if the embassy wasn't safe, nowhere was. News outlets reported that the embassy had been captured when in reality all of the attackers were soon lying dead in the courtyard.
Gen. William Westmoreland, the commander of the American forces in Vietnam, held a press conference at the embassy to announce that Tet was an American victory. But behind the general, dead Vietcong were still being dragged away from the blood-spattered lawn. Reporters could scarcely believe what they were hearing. Said one: ''Westmoreland was standing in the ruins and saying everything was great.''
Second, Eddie Adams's photograph of South Vietnam's police chief executing a Vietcong captive in the street caused a sensation. After he fired the shot, the police chief told nearby reporters: ''They killed many Americans and many of my men. Buddha will understand. Do you?'' Back home in the United States, the image spoke powerfully of a brutal and unjust war. For some Americans, this image was the Tet offensive.
Finally, the American news media painted a picture of disaster in Vietnam. Even though communist forces incurred enormous losses, reporters often lauded their performance. As the Times war correspondent Peter Braestrup put it, ''To have portrayed such a setback for one side as a defeat for the other -- in a major crisis abroad -- cannot be counted as a triumph for American journalism.''
A similar story later unfolded in Somalia. From 1992 to 1994, the American humanitarian intervention in Somalia saved the lives of more than 100,000 Somalis and cut the number of refugees in half, for the loss of 43 Americans. Back in the United States, however, this noble mission was widely viewed as the greatest foreign policy disaster since Vietnam. By October 1993, approval for President Bill Clinton's handling of Somalia fell to 30 percent. Only 25 percent of Americans viewed the intervention as a success, and 66 percent saw it as a failure.
Like Tet, the mission in Somalia suffered from overblown expectations. Intervening in an anarchical, war-ridden country was bound to be difficult. But early efforts to provide food and security in Somalia went so well that the project looked deceptively easy. The American public and news media lost interest -- until early October 1993, when American soldiers were killed in the infamous ''Black Hawk Down'' battle in Mogadishu.
With echoes of Saigon in 1968, powerful images of the Mogadishu battle pushed Americans towards a perception of defeat. Press coverage was dominated by pictures of the captured pilot, Michael Durant, and mutilated American corpses, often with the tagline of America's ''humiliation.'' Journalists tended to ignore the bigger picture, in this case large pro-American demonstrations in Somalia and successful efforts to save lives and restore order outside of the capital.
Memories of Vietnam, and fears of getting bogged down in another messy quagmire, also promoted perceptions of failure. In October 1993, 62 percent of Americans thought that the intervention in Somalia ''could turn into another Vietnam,'' even after Mr. Clinton announced that America was pulling soldiers out of Somalia, and at a time when American casualties were a thousand times lower than in Vietnam.
What does this mean for Iraq? At the least, Tet and Somalia suggest we should be very careful before concluding that Iraq is a defeat. There is real evidence of failure, especially the escalating sectarian violence. But our perceptions are nevertheless easily manipulated. Iraq looks like a defeat in part because the Bush administration fell into the same trap as President Johnson: raising expectations of imminent victory by declaring ''mission accomplished'' before the real work had even begun. And as with Somalia, fighting shadowy insurgents in Iraq while propping up a weak government engenders negative memories of Vietnam.
Perceptions of success and failure can change the course of history. Reeling from the supposed disaster at Tet, the United States began to withdraw. Memories of ''failure'' in Somalia were a major reason -- perhaps the major reason -- that the United States did nothing to stop the genocide in Rwanda in 1994. If Iraq is perceived as a failure, it is only a matter of time before America pulls out, leaving who-knows-what behind. With the stakes so high, Americans must be certain that their perception of failure in Iraq is not a mirage.
Dominic Johnson, a fellow at the Woodrow Wilson School of Public and International Affairs at Princeton, and Dominic Tierney, an assistant professor of political science at Swarthmore, are the authors of Failing to Win: Perceptions of Victory and Defeat in International Politics.