Every war has an end. And every limited war, of which Iraq like Korea and Viet Nam before it is one, reaches a point at which one (and sometimes both) of the parties finds a way to convince itself that it has achieved its objectives and can begin the process of disengagement. While many believed we were at that point a year or two ago with Iraq, the facts on the ground are so clear now that even Bush will be forced to accept that the time has come. The only question is when to begin the process of disengagement. Odds are that it won't begin until after the election.
This is a political decision, not a military one. Yes, the sequencing of the disengagement steps are largely dictated by the force protection needs of the military. However the decision to begin the process is purely political. In this case it is not small "p" political, as in how it affects the well being of the country, but big "P" political, as in how it affects the upcoming election.
(By way of full disclosure this is all speculation. Also, I was opposed to this war, unlike the Gulf War, a year before it began. I did not see Iraq as an enemy of the U.S., believed the war to be illegal, and believed we would only sow more chaos in an already unstable region. And when we were first informed that the insurgency was in its last throes I called for withdrawal here.)
Some people may be thinking that Bush will make a withdrawal announcement before the election to stem the growing tide of anti-Iraq war sentiment before the votes are cast. The stakes could not be higher. He knows there is a serious risk that one or both Houses of Congress could revert to Democratic control, in which event the many scandals and Constitutional outrages that his compliant enablers in the Republican Congressional leadership have kept out of sight will be exposed for the public to see. While that is clearly an outcome he is seeking desperately to avoid he will continue his "stay the course" strategy because he believes that to change course before the election will only cement his defeat. This is one of those rare occasions where he is right.
Bush is a one trick pony. That trick is fear. He has been very effective playing the fear card and is only now beginning to understand that it has lost much of its salience. People are becoming less willing to buy it, as evidenced by his failure to get a bounce from the alleged British plane bomber threat. But it is still his only card. He has to play it for all its worth between now and the election for one simple reason. If he announces now that we can begin to withdraw he will be conceding that Iraq is unwinable and in the process cut the rug out from under his remaining supporters. At that point, the Democratic election victory would become a true landslide.
The only real question is whether he will actually begin the disengagement process after the election, leave it to his successor, or wait until it is mandated by the Congress. If you listen to his rhetoric and watch his behavior there is reason to doubt he will withdraw voluntarily. He is so incapable of admitting error publicly that one must suspect he can barely do so in the sanctity of his own mind. We also have his public statements to the effect that the Iraq war will continue past his Presidency. Lastly, he gives every evidence that he has bought into the neocon mantra of the "long war" as the substitute for their much missed cold war.
However, he is a political animal and the political pressure he will be getting from his own party will be enormous. (This doesn't even factor in the potential impact of a Democratic victory in November.) His own party will tell him that if we are not substantially disengaged from Iraq in 2007 with the process complete in 2008 it will be decades before the Republicans will survive the electoral tsunami in 2008. By then Republican nominee will be touting his own plan to end the war, but it will be too late.
The tragedy of all this is how unnecessary it was. We have destroyed the lives of thousands of our soldiers and their families; set loose forces that have killed and injured hundreds of thousands of Iraqis; destroyed American credibility, goodwill and standing throughout the globe, spent hundreds of billions of dollars that are desperately needed at home; saddled our children and grandchildren with a mountain of debt; and destroyed the military that took so long to rebuild after Viet Nam. And it will only end because of partisan political necessity. How truly sad.