In December 2003, when I first convened a small task force to consider U.S. strategy in Iraq, public opinion toward the war and the subsequent military presence was strongly favorable. Saddam Hussein had just been captured, his sons Uday and Qusay were dead, and most of the members of the deck of cards had been rounded up. Few people knew anything about Abu Musab al-Zarqawi, let alone Muqtada al-Sadr.

Our conclusion, that it was in the U.S. strategic interest to terminate the military presence in Iraq at an early date, was so at odds with conventional wisdom at the time that it was clear that we were guided by certain core assumptions that set us apart from the policy community and from the public at large. The most important of these different assumptions was our sense that the risks posed by a long-term military presence in Iraq were very great, and the likelihood of success, as defined by the president, was very small. We also doubted that American security objectives were being advanced by the U.S. military presence in the country.

In retrospect, our call for a swift military withdrawal from Iraq, to be initiated immediately and completed by the end of 2004, was premature only in the sense that the American public did not yet share our skepticism. By late May 2004, when the final draft of our report went to press, withdrawal was not on the agenda. In the foreword to Exiting Iraq: Why the U.S. Must End the Military Occupation and Renew the War Against Al Qaeda, I wrote:

The Bush administration argues, “We must stay as long as necessary.” Many people quibble over what is “necessary,” but most implicitly endorse an open-ended commitment. In contrast, the authors of this report are unified in their opposition to the presumption that “we must stay.”

In the nearly two years since I wrote these words, a number of people have come forward to challenge the notion that we must stay. The frustrating lack of progress in Iraq has engendered considerable skepticism.

Barry Posen documents several of the more important failures in his insightful essay. The insurgency has hardly diminished and “is now reckoned to be three to four times what it was in the autumn of 2003.” Iraqi politics are rife with corruption. The performance of Iraqi security forces has been “mixed at best.” But perhaps most troubling is the sentiment of the Iraqi people, a point which Posen does not raise. A poll commissioned by the British Ministry of Defense found that 45 percent of Iraqis believed that attacks on coalition forces were justified at least some of the time, and a staggering 82 percent were “strongly opposed” to the presence of foreign troops.

Prompted by a lack of demonstrable progress in Iraq, the drip of skeptical essays and impudent questions (How long are we going to be there? How are we measuring progress? Why do so many Iraqis resent our presence? Why has the political process not contributed to a reduction in violence?) grew first to a trickle and then to a torrent. The most important questions address the present and the future.

The present is known: there are more than 150,000 U.S. troops in Iraq, and they are risking their lives every day. The future is unknown, even by the commander in chief: in his speech to the midshipmen at the Naval Academy on November 30, President Bush emphatically declared that he would not commit to a timetable for the withdrawal of troops. The mission in Iraq will be dictated by events on the ground, he explained, and it is therefore impossible to know when U.S. troops can leave.

Posen’s fine piece is based on a view that I share: the United States must know, and the Iraqis must know, and the world must know when the U.S. military mission in Iraq will end. Posen accurately frames the central question: Does the U.S. military presence, on balance, advance U.S. security objectives in Iraq? He also documents the various ways in which the U.S. presence impedes political progress and inadvertently fuels the insurgency. I concur wholeheartedly with his conclusion that “The American presence produces at best a bloody equilibrium, the endless cost of which will be paid by American soldiers and taxpayers.” This leads to a second question: Could a sizable military presence be reconfigured in such a way that it will serve America’s strategic interests? Again, I think the answer is no. Posen seems to agree.

Given that the U.S. military presence is harmful to American security interests, and given that it is unlikely that a slightly different military strategy can turn the tide, there is only one logical alternative: disengagement from Iraq within 18 months. Posen arrives at this conclusion by focusing on the likely costs and anticipated benefits of withdrawal for the United States. His treatment of America’s presumed moral and ethical obligations is excellent. He skillfully debunks the worst-case scenarios deployed by the president and his supporters, such as Iraq becoming a terrorist haven if the United States leaves. In his speech to the Naval Academy midshipmen, the president warned that al Qaeda “would then use Iraq as a base from which to launch attacks against America.”

Posen is appropriately more skeptical. We cannot be certain that a civil war, if one were to occur, would be a strategic boon for al Qaeda, and we need not have 150,000 troops in Iraq to ensure that it does not. “The most likely military outcome of this civil war is a stalemate, and this is what the United States should aim for,” Posen writes. I agree. Likewise, I agree with Posen’s assessment that the administration’s “assertion that the announcement of a definite date for the disengagement of American ground troops would be favorable to the insurgency is simply speculation,” made in order to “silence debate and discourage systemic analysis.”

Posen, to his great credit, cannot be silenced. He delivers a concise and convincing case for withdrawal from Iraq based on a clear-headed and dispassionate assessment of U.S. strategic objectives in the country. Withdrawal has never been a panacea, and it never will be. We are confronted as a nation with a set of unpalatable options, but the complete withdrawal of U.S. forces represents the least bad of the lot. If we do not specify an end date, a point after which we can be certain that the American military and the American public will no longer be responsible for Iraqi security, then we are left as a nation at the mercy of events beyond our control, and in a few years’ time we may find that we have even fewer choices at our disposal.