Some troops head home, but more must stay in Iraq
A US force of 60,000 or more will be needed to help build a stable nation.
With top military commanders declaring this week that the heavy fighting in Iraq is over, a top concern for many Americans is getting US troops home.
Stealth bomber pilots and aircraft carrier personnel are already heading back to the US.
But for soldiers and marines on the ground - who overcame enemy fire, fatigue, and the fear of guerrilla attacks to win a decisive victory - a stubborn fact lies between them and their loved ones at home: Their country needs thousands of them to stay on to maintain order until a new Iraqi government takes shape.
The current combat units will remain on the ground for at least several more weeks. And new Army units continue to arrive.
Keeping the peace in Iraq will require a force of between 60,000 to 75,000 US troops for at least six months, military experts say. If looting spreads, fighting breaks out between rival clans, or neighboring countries seek to infiltrate Iraq's porous borders, the force could double and the commitment could stretch into years.
"More troops will be needed to quell the trouble," says Chris Seiple, a former Marine Corps officer and peacekeeping specialist at the Institute for Global Engagement in St. Davids, Pa.
But even the rosiest scenario commits the US to deploying a far larger share of its strength to the region than any estimate suggests, since for every soldier to be based in Iraq, another will be preparing to ship out and a third recovering from duty.
Perhaps 20,000 troops would be needed to secure each of the north, central, and southern parts of the country, says retired Marine Lt. Col. Noel Williams, now a research fellow at the Marines' Center for Emerging Threats and Opportunities.
Three additional brigades of about 5,000 troops each would be needed to secure Iraq's borders with Turkey, Syria and Iran. Those numbers reflect norms for civilian policing in the US (2.3 sworn officers per thousand of population) and stable peacekeeping operations such as the US occupation of Germany after World War II.
But more volatile interventions such as the Punjab region of India or Northern Ireland have required as many as 20 officers per thousand.
The boot count may vary depending on the region. More soldiers might be needed in the north to assuage Turkish concerns about Kurdish independence.
The flat desert terrain along the Syrian border means technology can easily supplement eyes on the ground. JSTARS aircraft, designed to locate enemy tank movements, could also track car and truck traffic. The US is also turning to local police to jointly patrol streets.
If Iraq can be stabilized quickly, experience in postwar Japan and Germany suggests the force could be rapidly drawn down. In Germany, the US replaced nine divisions with a single division of constables five months after the Nazi surrender, says Stephen Henthorne of the US Army Peacekeeping Institute.
In the best case scenario, the US presence might be reduced to three brigades totaling about 15,000 troops after six months with National Guard troops gradually replacing combat troops, suggests retired Lt. General Charles Otstott.
National Guard brigades have served effectively as peacekeepers in Kosovo and Bosnia, but require months of training before they are ready for duty abroad.
Elements of other Army combat forces - including the 4th Infantry Division and 2nd Armored Cavalry Regiment - are beginning to arrive in Iraq to provide reinforcements and allow exhausted combat units to disengage.
The 1st Armored Division based in Germany is also slated to deploy.
Special Operations units, trained for close contact with communities and quick response, are well-suited to help, says Seiple. Another alerted unit, the 10th Mountain Infantry Division, kept peace in Haiti and Kosovo but its current troops didn't necessarily serve in either place.