Under that scenario, we can expect Iran -- already a regional power -- to support the Shiite Muslims in the south, a move that would give Tehran control of most of Iraq’s oil. Not that this would necessarily keep the oil flowing; as the civil war escalated, guerrillas would cut pipelines and blow up oil wells.

Right now, Iraq produces 2.5 million barrels of oil per day, and the country’s government aims to increase that to 2.7 MBD by year’s end. If production is disrupted, though, worldwide prices would skyrocket.

If we cut and run, Iraqi civilians would be the biggest losers. Millions would flee the starvation, disease and destruction that civil war brings. Meanwhile, al Qaeda would tout its role in forcing the U.S. out, providing a huge recruiting boom for the terrorist group.

This doesn’t mean we should stay indefinitely. As they say, there are only two “exit strategies” from any war: A country can win and go home, or it can lose and go home. Either way, all our troops eventually will exit Iraq. What really matters is what they leave behind.

We’ve made progress in Iraq, and we’ll continue to do so. Many of al Qaeda’s senior leaders have been killed or captured and the group’s popularity among the Iraqis is low. We need to keep training Iraqi forces and preparing them to stand on their own.

In the long run, only Iraqis can assure the success of Iraq. But if, in the short run, we cut and run, we guarantee failure -- for them and for us. We can avoid the bleak future outlined above. But we must steel our resolve to get the job done right.