Dominoes are back. The old, scuffed political theory of one domino falling and knocking down others turned up recently in President Bush's call for support from Congress for a surge in U.S. troops in Iraq.

On March 19, Bush said: "If American forces were to step back from Baghdad before it is more secure, a contagion of violence could spill out across the entire country. In time, this violence could engulf the region. For the safety of the American people, we cannot allow this to happen."

The domino theory, however, contains inherent flaws. It conflates present or past events with projection into the future. More symbolic than analytical, it predicts that outcomes will be worse unless new actions are taken. This reinforces an argument for sustained or escalated military involvement.

Why make such a case today? Simple: it works. Wartime presidents of both parties have historically recognized the value of domino theory and used it to support continued military intervention.

Consider past precedents. Born in the early Cold War years, under President Harry Truman, the domino theory found acceptance by his successor, general-turned-president Dwight D. Eisenhower. "You have a row of dominoes set up," said Ike in 1954, "you knock over the first one and what will happen to the last one is the certainty that it will go over very quickly. . . you could have a beginning of a disintegration that would have the most profound influences."

Adopted to justify the American entry into Indochina, this assumption underlay the rationales of Kennedy, Johnson, and Nixon in escalating the Vietnam War. As Johnson explained in 1967: "We have chosen to fight a limited war . . . in an attempt to prevent a larger war - a war almost certain to follow, I believe, if the Communists succeed in overrunning and taking over South Vietnam by aggression and by force."

President Bush expands on this theory by calling for a drive to spread freedom and democracy throughout the Middle East. He echoes the words of Johnson and Eisenhower, declaring that the "challenge playing out across the broader Middle East is more than a military conflict. It is the decisive ideological struggle of our time."

Some ask: If it were so decisive why not use overwhelming force? And why continue to use force if the struggle is extra-military? In his State of the Union Address in January, Bush responded to such criticism: "In the long run, the most realistic way to protect the American people is to provide a hopeful alternative to the hateful ideology of the enemy - by advancing liberty across a troubled region."

Just as with Eisenhower, Bush's rhetoric is shot through with contradictions. Ike proclaimed with "certainty" that the "last" domino would fall if the first one did; however, he also noted this to be a "possible sequence of events." Bush likewise hedges his words. While terming the clash "decisive," he asserts only that the "contagion of violence" "could" spill out of Iraq. Decades after the Vietnam War, our national leaders are using the same discredited arguments to justify an expanded American presence in Iraq.

Remarkably, the domino theory also has become part of jihadist doctrine. A psychiatrist and the Al Qaeda mastermind of the Madrid bombings, Dr. Abu Hafiza, wrote in 2004: "After knocking over one domino after another, we will stand face to face with the key domino, the United States." The sheer absurdity of such an outcome makes the assertion laughable. Yet it causes fear. And fear forms the basis for domino theory.

As military and political history amply illustrate, the domino theory falls flat. To be sure, America's departure from South Vietnam was horrific. U.S. allies there suffered terribly. So did the United States as a whole. Global prestige plummeted. A chastened America became less likely to engage in hot wars. Cambodia and Laos turned communist.

Nonetheless, the domino theory failed by the standard of its own predictions. Communism never took hold in Indonesia, Thailand, or more importantly, in any of the other large countries in the region, most notably, India. There was no cascade effect triggered by the U.S. departure from South Vietnam. The United States continued as an economic and military power. And now, America and Vietnam are trading partners, which President Bush should know as he visited that nation last year. Southeast Asia is a vibrant engine of global commerce and the region has closer ties to the United States now than at any time in the past.

Sometimes an action, however terrible, is an isolated event. It may not have irrevocable ramifications, much less disastrous ones. The concept of nation-state dominoes toppling in a row does not accurately describe the reality of the non-state actors engaged in modern 21st century terrorism. Nor does it apply to the divisive nature of the sectarian civil war in Iraq. It cannot.

The withdrawal of U.S. forces from Iraq is likely to have horrendous consequences on the ground. Humanitarian concerns must be addressed. Yet when seen in a longer historical view, such an event might not be nearly as tragic as predicted. It may result in unforeseen, long-term positive effects. At the very least, it seems unlikely that it will lead to a catastrophic crescendo of crumbling governments.

The President should put the dominoes back in the box.