WASHINGTON -- Before Gen. David Petraeus' report, and to give it a context of optimism, the president visited Iraq's Anbar province to underscore the success of the surge in making some hitherto anarchic areas less so. More significant, however, was the fact that the president did not visit Baghdad. This underscored the fact that the surge has failed, as measured by the president's and Petraeus' standards of success.

Those who today stridently insist that the surge has succeeded also say they are especially supportive of the president, Petraeus and the military generally. But at the beginning of the surge, both Petraeus and the president defined success in a way that took the achievement of success out of America's hands.

The purpose of the surge, they said, is to buy time -- "breathing space," the president says -- for Iraqi political reconciliation. Because progress toward that has been negligible, there is no satisfactory answer to this question: What is the U.S. military mission in Iraq?

Many of those who insist that the surge is a harbinger of U.S. victory in Iraq are making the same mistake they made in 1991 when they urged an advance on Baghdad, and in 2003 when they underestimated the challenge of building democracy there. The mistake is exaggerating the relevance of U.S. military power to achieve political progress in a society riven by ethnic and sectarian hatreds. America's military leaders, who are professional realists, do not make this mistake.

The progress that Petraeus reports in improving security in portions of Iraq is real. It might, however, have two sinister aspects.

First, measuring sectarian violence is problematic: The Washington Post reports that a body with a bullet hole in the front of the skull is considered a victim of criminality; a hole in the back of the skull is evidence of sectarian violence. But even if violence is declining, that might be partly because violent sectarian cleansing has separated Sunni and Shiite communities. This homogenization of hostile factions -- trained and armed by U.S. forces -- may bear poisonous fruit in a full-blown civil war.

Second, brutalities by al-Qaeda in Iraq have indeed provoked some Sunni leaders to collaborate with U.S. forces. But these alliances of convenience might be inconvenient when Shiites again become the Sunnis' principal enemy.

Congressional Democrats should accept Petraeus' report as a reason to declare a victory, one that might make this fact somewhat palatable: Substantial numbers of U.S. forces will be in Iraq when the next president is inaugurated. The Democrats' "victory" -- a chimera but a useful one -- is that Petraeus indicates there soon can be a small reduction of U.S. forces. Continued...