Members of Congress are divided over when to begin a major drawdown of U.S. troops in Iraq. But there is near-unanimous agreement over what could happen in the absence of a large U.S. military presence: chaos.
Still, experts differ on just what impact that chaos would have on U.S. national security.
President Bush has argued repeatedly that if U.S. troops leave Iraq anytime soon, "the consequences for America and the Middle East would be disastrous." He says fighting could engulf the region, and he warns of the emergence of an al-Qaida base in Iraq from which to launch new attacks against America.
"If we fail in Iraq, Mr. Bush says, "the enemy will follow us home."
James Carafano shares the president's concerns. He's a retired Army lieutenant colonel and now a military analyst at the conservative Heritage Foundation.
Carafano believes an early withdrawal of U.S. troops from Iraq would lead to a bloodbath.
"The best-case scenario," he predicts, is that "after hundreds of thousands are displaced, tens of thousands killed, the country is totally destitute — like Rwanda on steroids."
Carafano agrees with the president that Iraq could become a terrorist sanctuary. But many other experts, both in and out of government, disagree.
"That horse has already left the barn," argues Thomas X. Hammes, a retired Marine colonel and professor at the National Defense University. Hammes says Iraq-trained or Iraq-inspired terrorists have already carried out attacks in places such as London, Spain and Bali.
The recent terror attack at Glasgow airport is a case in point, he says.
And Ray Takeyh, an Iran expert at the Council on Foreign Relations, says the White House presents the best evidence to the contrary.
"One of the indications of success that the administration is presenting is that in Anbar province, the Sunni tribes are beginning to turn against al-Qaida," Takeyh notes. "So the idea that an American withdrawal will lead to an al-Qaida sanctuary in northwest Iraq is belied by the evidence that the administration is itself presenting."
Takeyh also takes issue with White House predictions of a full-scale regional war.
He says Iraq's neighbors have every interest in preventing war from spilling over their borders. "Instead of ... intensifying their presence and exacerbating the civil war, they may actually [get] involved in a serious mediation effort," says Takeyh.
The problem, of course, is what happens in the interim — in the period between a U.S. pullout and a regional response. Most people looking into the possibiilties predict an internal war far bloodier than the one taking place now. That's something the American government — and by extension, the American public --will have to be prepared to witness.
In the meantime, the Pentagon is conducting a series of war games to try to predict what might happen when the U.S. leaves Iraq. The U.S. military must begin scaling back its mission in Iraq by April 2008. The reason: The Army will start to run out of available manpower by that point.