From what we know (or at least from what I know) about the complex situation in Iraq, the war will not end or cannot be ended in the first way. Neither U.S. forces nor insurgent forces can decisively defeat the other in order to force it to surrender.
Can it end the second way? What would it take?
The most important determinant is the appreciation by decision makers on both sides that a condition of military deadlock has been reached, coupled with their judgments that the chances of favorably altering the military balance of power on the field of battle are slight or nonexistent, or that the effort will be too costly in relation to some standard of cost-effectiveness. In this instance, decision makers have decided that a compromise armistice will better serve their reduced aims, offer more hope of achieving their goals in the long run, or at least lessen the heavy human, material, and political costs of continued war.
It may all come to this, but it does not now appear that the players (the heterogeneous insurgents, the interim government, or the Bush administration) have yet reached this point. The moment might come, however, if and after the new constitution is adopted and elections are held. Bush might then, for example, adopt Nixon’s Vietnamization/decent-interval exit strategy, coupled with negotiations.
The third type of war ending seems unlikely, unless the warring parties agree to some sort of UN or international intervention.
Meanwhile, civil war looms.