More than six years after invading Iraq and deposing its leader, Saddam Hussein, U.S. combat forces have withdrawn from Iraq's cities. The redeployment is an important step forward in the reclamation of Iraqi sovereignty, and a political victory for Iraqi Prime Minister Nouri al-Maliki.

The move is not a complete withdrawal, however. U.S. forces have been moved outside the cities and can return if requested. Trainers and advisers also remain in the urban areas. The question now is whether Iraq's security forces can keep the peace — not only against insurgents who oppose Mr. al-Maliki but also by preventing sectarian violence against the Sunni minority.

The clock has been ticking toward a U.S. withdrawal since then U.S. President George W. Bush launched the "surge" — a massive influx of American combat forces to stabilize Iraq — in May 2007. After an initial and expected spike, violence in Iraq has diminished, allowing the Baghdad government to consolidate its own power and authority. The election of Mr. Barack Obama, who had campaigned on a pledge to withdraw U.S. forces, provided a new urgency to the Iraqi task of taking responsibility for the country's security.

Agreement was reached late in 2008 on a timetable for the U.S. withdrawal. The first milestone in that process was the June 30 redeployment. The second is a referendum on a bilateral U.S.-Iraq security pact, scheduled to be held this month. A complete withdrawal of the 130,000 U.S. forces that remain in Iraq is supposed to be complete by January 2012.

That is if all goes as planned. Delays look likely. Baghdad wants to postpone the July vote until January 2010 and hold it along with a parliamentary ballot, arguing that it is impossible to organize a referendum in less than a month and insisting the government cannot afford the $100 million price tag for a one-vote national ballot. If the referendum on the security pact is not approved — whenever it is held — then U.S. forces could be gone within a year of its rejection.

The biggest question about the future is whether the Iraqi security forces can keep the peace. Military and political officials in both Iraq and the U.S. have expressed confidence that Iraqis can do the job, but that is to be expected. They are unlikely to challenge a policy in which both leaderships have big investments.

In the runup to the redeployment, violence mounted. Insurgent attacks claimed the lives of 447 Iraq civilians in June, two times the number killed the previous month. Staggering though that toll may be, it is still much lower than in previous years. By one estimate, war-related violence resulted in 1,902 deaths in the first six months of 2009 vs. 4,809 deaths in the same period in 2008. The ramped-up campaign by suspected Sunni extremists did not trigger retaliatory attacks by Shiite militias as in the past. It is unclear whether the violence was intended to slow or halt the move by U.S. forces or was a bloody farewell to the Americans.

Mr. al-Maliki seeks to capitalize on the handover and the new security situation as a way of consolidating his grip on power and preparing for the January parliamentary vote. His chief rival, cleric Muqtada al-Sadr, has led calls for a complete U.S. withdrawal and sees things differently — as do other critics of the prime minister. Those critics call the redeployment a victory for militants — which they purport to lead — and dismiss the government's claim that the U.S. pullback is a vote of confidence in Baghdad. The opposition aims to create enough violence to undermine the government's legitimacy without triggering calls for the U.S. forces to return.

Several prominent members of the opposition disagree with the aim. Hoping to head off a descent into sectarian violence and civil war, they have urged their followers to avoid targeting fellow Iraqis. For them, the real enemy is the continuing U.S. presence, whether political, military or economic. The remaining American forces are hard targets, however, and frustration might drive the militants to focus on civilian targets to make their point that Baghdad is indeed too weak to protect its citizens.

There are forces in Iraq that are indifferent to the civilian toll they take. Al-Qaida has a presence, too, and could focus its energies on destabilizing the Baghdad government and keep the U.S. tied down in Iraq. That tactic failed in the past when local Iraqis recognized that al-Qaida had its own agenda, one that did not align with those of their country. Their decision to turn on al-Qaida forces was a key factor in the success of the surge.

A similar recognition of where Iraq's true national interests lie — in the creation of a stable and peaceful country that offers security and prosperity to all its citizens — would ensure that the U.S. redeployment is a genuine milestone in Iraq's history and not another missed opportunity.