While the U.S. military reports on securing Fallujah, a leaked memo from senior Marine Corps officers on the scene warns against premature withdrawal of American forces. The “brutally honest” seven-page report went to senior Marine Corps and Army officers in Iraq. The New York Times said it learned details of the report from four active-duty or retired military officers in Washington and Iraq who had read or heard about it.

U.S. forces in Iraq are stretched thin as they face a growing and increasingly sophisticated insurgency, even though the present 140,000 total has been beefed up by delaying the return home of some troops scheduled for rotation. Training of Iraqi police and National Guard units to take their places has taken longer than expected, and their performance has sometimes been disappointing.

Hundreds of U.S. troops have already been withdrawn from Fallujah and reassigned to other trouble spots such as the northern city of Mosul.

The leaked warning said that the insurgents, despite heavy casualties in the battle, would continue to recruit resentful residents, and make guerrilla attacks. The situation in Fallujah is beginning to follow a familiar pattern in which U.S. forces recapture a city seized by the rebels, move on to other insurgent strongholds, and then find out that the rebels have returned and gathered strength.

Headquarters officers brushed off the warning as a subjective judgment and a “worst-case assessment.” But such gloomy appraisals have sometimes proved prescient in the Iraq war, starting with doubts that Iraqis would welcome the invading Americans and that pacification would be a relatively easy matter. The new warning actually echoed the words of Gen. George W. Case, Jr.

The Times quoted the top American commander in Iraq as having said on Nov. 8, “It will take a security presence for a while until a well-trained Iraqi security force can take over the presence in Fallujah and maintain security so that the insurgents don’t come back, as they have tried to do in every one of the cities we have thrown them out of.”

Leaked documents like this one can be a helpful balance to rosy official reports and private directives such as the one from the new intelligence chief, Porter J. Goss, that intelligence officers should never talk with the press or members of Congress. We know about this because it, too, was leaked.

One of the great things about our open American society is that truth generally will out.

Whistleblowers have become institutionalized in government and corporate life. They go public and enjoy legal protection against retaliation.

Leakers, who have no such protection, demand anonymity. Watergate became known when honest bureaucrats saw that the Nixon administration was using pressure and bribery to fix a criminal investigation and gave details to The Washington Post. The pattern goes back to the Teapot Dome scandal of the 1920s. Leaks, such as the memo on Fallujah, can give insight and understanding that official reports too often avoid.