Bush signaled no shifts in policy, as Democrats such as Sens. Joseph R. Biden Jr. (Del.) and John F. Kerry (Mass.) have called for in recent days. Instead his goal was to reeducate Americans on his view of the stakes involved in Iraq and the consequences to the Middle East and U.S. security if the insurgents prevail.

President Bush's speech in many ways mirrored one he gave a year ago on Iraq. Last night he called the war there "difficult and dangerous." (By Charles Dharapak -- Associated Press)

His clearest message was to argue anew that Iraq is the critical battle in a war against terrorists that began with the attacks of Sept. 11, 2001. He made repeated references to those attacks to underscore that U.S. security depends on defeating the insurgency in Iraq. "After September the 11th, I made a commitment to the American people," he said. "This nation will not wait to be attacked again. We will defend our freedom. We will take the fight to the enemy." He then added, "Iraq is the latest battlefield in this war."

Sept. 11 remains Bush's most reliable argument with the public when he faces political headwinds; it gave him the highest-rated moments of his presidency and helped sustain him through a difficult reelection campaign. Surprisingly, given how effectively he has used the collective emotion of that day in the past, Sept. 11 has been largely missing in the administration's discussions of Iraq this year.

His critics long have accused Bush of falsely drawing a connection between Iraq and Sept. 11 as a way to justify the original decision to launch the war in Iraq. That was not the point Bush made last night. Instead it was that Iraq has now become such a magnet for foreign terrorists that winning the current battle there is every bit as critical as was the fight to depose Saddam Hussein.

With public opinion persistently negative on the president's decision to go to war, administration officials are concerned that, without clear leadership on Bush's part, Americans will turn even more gloomy about the road ahead. The question now is how long the public will tolerate continued deployment of U.S. forces in a conflict with a future that appears both bloody and enormously difficult.

The stakes for Bush could hardly be higher, given the reality that unpopular wars can lead to the unraveling of a presidency. Bush's lofty ambitions for a free, stable and democratic Iraq may stir Americans' sense of idealism, but if events on the ground call those goals into question, the potential for erosion in support remains significant.

No single speech can cement public opinion, particularly in a conflict in which the administration has been guilty of misjudgments about the strength of the opposition and the timetable for stabilizing and rebuilding Iraq. To a surprising degree, given the strength of the insurgency in Iraq, Bush has maintained support for the broad goals of his Iraq policy and for a continued military presence there. But nothing guarantees continued support if there is little sign of progress on the ground.

Administration officials said the key to sustaining support is to convey a sense of reality about the difficulties ahead while demonstrating a determination to win the war no matter what it takes. Bush argued last night that, despite apparent setbacks in Iraq, the country is moving inexorably toward democracy, but it is a message that has been missing from the White House bully pulpit for most of the year and forced him back to where he was a year ago.

It was 13 months ago, at a time of grisly beheadings and mounting U.S. casualties, that Bush went to the U.S. Army War College in Pennsylvania for a prime-time speech on Iraq with much the same mission as he had last night. In that speech, he called Iraq the central front in the fight against terrorism and said victory would deal a decisive blow to terrorists. He said the United States was making progress but there was much work left to do.

Last night, from Fort Bragg, N.C., his words sounded extraordinarily similar. He called the battle in Iraq, still described as the main front in the fight against terrorism, "difficult and dangerous." He said he is as repelled by the bloodshed as ordinary Americans watching the violence on their television screens at home, but he argued that the sacrifice is worth the price. The terrorists can win, he said, only if Americans "forget the lessons of September 11th."

In the year between those speeches, Iraq has taken steps toward forming a democratic government, most notably through the elections there in January. But the steps have been slow and halting at times, and the Iraqis face huge hurdles in trying to meet the deadline of writing a constitution by later this summer.

On the ground, little seems to have changed. After a decline around the time of the Iraqi elections in January, U.S. casualties have increased again this spring. Iraqi civilians are dying at higher rates than a year ago, and the number of car bombings has risen from 18 in June 2004 to 135 last month. Reconstruction has been halting. According to the Brookings Institution's Iraqi Index, monthly production of crude oil has not risen in the past year, nor has the reliability of electric power. Electricity nationwide was available on average for 8.4 hours per day in May, according to the report.

Bush sought to assure Americans that his plan for training Iraqi security forces is moving forward, saying more than 160,000 of them have "trained and equipped for a variety of missions." Last week, Biden said that only about 2,500 of those troops are capable of operating independently and that it will take two more years to build a fully functioning Iraqi army.

Given that record, it is not surprising that Bush's approval ratings on Iraq have sagged throughout the spring. Bush has spent months touring the country to promote a Social Security restructuring plan, at the expense of his Iraqi policy. Administration allies worry that without more vigorous presidential leadership, a growing chorus of critics in Congress could cause a more significant erosion in public opinion.

What may be surprising is the degree to which people continue to support maintaining a sizable U.S. military presence in Iraq in the face of such little progress in the past year. Polls offer conflicting conclusions about sentiment toward withdrawing troops, with some surveys suggesting that patience already has begun to wane. A new Washington Post-ABC News poll, however, finds that only 13 percent of those surveyed said it is time for U.S. forces to get out.

John Mueller, a professor of political science at Ohio State University, said Bush is lucky that support for the war is not even lower. "I would have thought intuitively it would be lower because the main reasons for going to war have been wiped out," he said.

Andrew Kohut, director of the Pew Research Center for the People and the Press, said there is little doubt in his mind that without the connection to Sept. 11, calls for bringing the troops home would be far louder than they are. "Without a war on terrorism and people feeling a real threat, it would be like Vietnam," he said.

The fact that the public continues to support keeping troops in Iraq has made Democratic efforts to criticize Bush more difficult, as few Democratic leaders are calling for an explicit exit strategy. But it is congressional Republicans who may be most worried now about the course of events in Iraq. They, not Bush, must face the voters next year and they will become leading indicators of how effective the president has been in persuading Americans to stay the course.