Candidate Barack Obama's pledge to order the withdrawal of all American combat troops from Iraq in 16 months was a winner on the campaign trail, but it may turn out to be a tall order now that he is president. Fortunately, Mr. Obama gave himself some wiggle room on the timetable. It looks like he is going to need it.

“We're going to have some difficult decisions that we are going to have to make surrounding Iraq and Afghanistan, most immediately,” the president said this week after a two-hour discussion with the Joint Chiefs of Staff about closing down one war and widening another. Officials said afterwards that specific timelines were not laid out, but the president has already said publicly he would listen to the advice of his generals and adjust his deadlines if the safety of American troops or the stability of Iraq were threatened. That's a big “if.” Here's why.

The withdrawal of American troops entails great risks. It's not just the tactical problems of pulling tens of thousands of soldiers and their equipment out of potentially hostile territory. The biggest danger is the power vacuum they will leave behind them.

For the moment, Iraq is enjoying a relative calm. The Bush administration strategy of “surging” 30,000 American troops into Iraq and negotiating with Sunni insurgents has paid off handsomely. Violence has diminished by 80% in the past two years and is now limited to parts of Baghdad, Mosul and Diyala Province. But Lt. General Ray Odierno, US military commander in Iraq, warns that these gains are “fragile and reversible,” and that “The war is not over.” The fear is that if the Americans leave too quickly, the Iraqis will settle their quarrels among themselves once they are on their own.

That would not be a pretty sight because the Pentagon has not only armed thousand of Sunni insurgents. It has also trained and armed a quarter of a million Iraqi troops and half a million police. Many of them owe their loyalty to their religious sects or tribal clans, rather than to the American-backed government. Left to their own devices, they could easily turn against rival sects and clans.

In fact, none of the basic conflicts of Iraq have been resolved. They have simply been damped down by the American presence. The Kurds of the north still want independence. Kurds and Arabs still dispute control of the giant oil fields of Kirkuk. Moqtada al-Sadr's “Mahdi Army” has declared a truce but remains one of the most powerful sectarian militias in the country. The remnants of Al Qaeda in Iraq suffered a defeat when the Sunni insurgents turned against them, but have not left the country. And the former Sunni insurgents are itching to grab more power in the central government.

But if the aftermath of the American withdrawal may not be a pretty picture, it is also likely that the American public will not see much of the mess. Most American newspapers and broadcasters seem to have decided they don't want to hang around for the last act in Iraq. Many have already gone home, leaving behind only skeleton news bureaus in Baghdad, or increasingly, no one at all. Manning a Baghdad bureau is an expensive operation, and the corporations that own the news media clearly think the bottom line is more important than making an effort to keep the American public in the picture. The media failed to do their duty when they did not question the Bush administration's basic premise for going into Iraq. They will fail us again if they are not there to see what happens when the Obama administration pulls out.