"It takes time to snuff out the insurgency," Casey said. "And also, I think you know, most insurgencies are defeated by political means rather than necessarily by military means."
But Iraqi politics, along with the promise of fostering a permanent peace, also carry the threat of fomenting greater instability if accommodation cannot be reached among the country's Shiite, Sunni and Kurdish communities. With negotiations over establishment of a new administration dragging on, the euphoria that initially followed January's elections has given way to warnings that the lack of political agreement will result in new sectarian violence and terrorist activity.

A military recruiter exits his office in New York. Reducing U.S. troops in Iraq will turn on how fast Iraqi forces and police can be trained.
(Spencer Platt -- Getty Images)
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"I believe that uncertainty will almost certainly breed more violence," Army Gen. John Abizaid, the top U.S. officer in the Persian Gulf region, told the Senate Armed Services Committee recently.
He predicted political turmoil ahead, given the challenges this year of drafting a new constitution and electing a permanent national government. Such turmoil, he said, "will probably not allow the institutions to really get as established as we would like. So we have to be cautious in expecting that they will develop faster or more efficiently than we might expect."
In the meantime, U.S. commanders have placed added emphasis since the elections on the training of Iraqi security forces. The development of these homegrown forces has become the centerpiece of the Pentagon's exit strategy. The goal for the end of the year is to have Iraqi troops leading the fight against insurgents in most parts of the country.
But the progress of the mission has become a source of political dispute, with Democratic lawmakers calling into question the accuracy of administration assertions that 142,000 troops and policemen have been trained and equipped, out of a projected total of 271,000 by July 2006.
Pentagon officials concede the figures for Iraqi policemen are less accurate than the numbers for Iraqi soldiers, and they acknowledge that few of the units fielded so far are capable of operating independently of U.S. forces. In retrospect, they say, a series of missteps were made in initial efforts to develop the Iraqi forces, including sending them into combat last spring, ill-trained and poorly equipped.
But they contend solid progress is now being made in accounting for the forces, improving their training and bolstering their command structures.
With all the focus on the buildup of forces, some senior U.S. officers worry that other elements critical to defeating the insurgency will be overlooked, particularly the need for economic improvements.
"I fear, when I watch the news, that everyone is focused solely on fixing Iraqi security forces," said Maj. Gen. Peter Chiarelli, who commands the 1st Cavalry Division, which returned to Texas this month after a year in Iraq. "If this comes at the cost of not making the infrastructure improvements that need to be done, we'll create a bigger army but also a larger insurgency, which regenerates itself if you don't address the underlying grievances about basic needs not being met. People want jobs, they want their sewers fixed, they want fresh water."
Whatever the future holds, the story up to now of the U.S. occupation of Iraq suggests a number of surprises still in store.
"The experience of the last two years should make us cautious about claiming Iraq is on an irreversible course toward victory," said Peter Feaver, a political science professor who specializes in military affairs at Duke University. "To me, the remarkable thing is just how wrong everyone has been in predicting the twists and turns that have occurred so far."