Withdraw immediately or stay the present course? That is the key question about the war in Iraq today. American public opinion is now decidedly against the war. From liberal New England, where citizens pass town-hall resolutions calling for withdrawal, to the conservative South and West, where more than half of “red state” citizens oppose the war, Americans want out. That sentiment is understandable.

The prewar dream of a liberal Iraqi democracy friendly to the United States is no longer credible. No Iraqi leader with enough power and legitimacy to control the country will be pro-American. Still, U.S. President George W. Bush says the United States must stay the course. Why? Let’s consider his administration’s most popular arguments for not leaving Iraq.

If we leave, there will be a civil war. In reality, a civil war in Iraq began just weeks after U.S. forces toppled Saddam. Any close observer could see that then; today, only the blind deny it. Even President Bush, who is normally impervious to uncomfortable facts, recently admitted that Iraq has peered into the abyss of civil war. He ought to look a little closer. Iraqis are fighting Iraqis. Insurgents have killed far more Iraqis than Americans. That’s civil war.

Withdrawal will encourage the terrorists. True, but that is the price we are doomed to pay. Our continued occupation of Iraq also encourages the killers—precisely because our invasion made Iraq safe for them. Our occupation also left the surviving Baathists with one choice: Surrender, or ally with al Qaeda. They chose the latter. Staying the course will not change this fact. Pulling out will most likely result in Sunni groups’ turning against al Qaeda and its sympathizers, driving them out of Iraq entirely.

Before U.S....