Before a live-fire exercise at The Besmaya Combat Training Center on Tuesday, soldiers of an Iraqi Army platoon completing a 21-day course stand near a self-propelled howitzer purchased by Iraq from the United States as part of a "foreign military sales" package [caption has been corrected]. (Dan Zak/Washington Post)

The U.S. military closed the second of its three regional headquarters in Iraq on Thursday, redeploying 750 soldiers, consolidating command of nationwide operations under a single Army unit and maintaining a rapid pace of withdrawal 10 weeks before the expiration of its security agreement with Baghdad.

A ceremony at Contingency Operating Base Speicher, 110 miles north of the capital, honored the 4th Infantry Division for its year-long command of the north division of Iraq and marked the second deactivation of a headquarters unit within the past six weeks.

Gen. Lloyd J. Austin III, the commander of U.S. forces in Iraq, praised the troops’ training partnership with Iraqi forces in the region.

“As you well know, northern Iraq . . . is an area that greatly impacts security in other parts of the country, as extremist groups such as al-Qaeda have used the Tigris River Valley and other northern locations as staging areas to launch attacks,” Austin said. “It is also an area that offers great economic potential while at the same time presenting complex political challenges.”

The northern division, as defined under Operation New Dawn, includes the cities of Mosul and Kirkuk as well as Iraqi Kurdistan, whose borders with Iran and Turkey remain restive. As the U.S. military carried out its deactivation ceremony, 10,000 Turkish soldiers engaged in a ground offensive against Kurdish rebels who had attacked border towns Wednesday, the Turkish military said.

Lt. Gen. Robert L. Caslen Jr., the new commander of both NATO's and the United States's training missions in Iraq, and Iraqi army Lt. Gen. Babaker Zebari view live-fire exercises using howitzers at The Besmaya Combat Training Center on Tuesday. (Dan Zak/Washington Post)

An extended U.S. presence “is essential for Iraq because it needs to train its troops, especially in Kirkuk and in disputed areas,” said Kirkuk’s provincial governor, Najmaldin Karim, whose city’s ethnic tensions make it a tinderbox for conflict.

About 39,000 American troops remain in Iraq. At its peak engagement in 2008, the military staffed 505 bases with 165,000 forces. Eighteen bases remain under U.S. control; the rest have been decommissioned, ceded to Iraqi security forces or repurposed for civilian use. An average of 520 service members depart Iraq every day.

The void created by the drawdown in personnel and equipment is somewhat compensated for by foreign military sales to Iraq. The country is buying weaponry and training in bundled “cases,” or full-service packages, from the United States and other nations. About 400 cases, worth $10 billion, are being administered in the country, and an additional 110 cases, worth $900 million, are pending.

U.S. and Iraqi officials attended a demonstration of one such case Tuesday at the Besmaya Training Center, southeast of Baghdad. A regiment of Iraqi soldiers from Diyala province completed its 21-day artillery course with a live-fire exercise in front of Lt. Gen. Babaker Zebari, chief of staff of the Iraqi military, and Lt. Gen. Robert L. Caslen Jr., commander of the Office of Security Cooperation-Iraq, a three-week-old training entity overseen by the State Department. The office is quickly assuming control of Iraq operations from the U.S. military.

A platoon of three M1A1 tanks fired rounds at short- and long-range targets as officers watched from a shaded grandstand.

“That’s a big hole,” Caslen said, viewing the distant bursts of smoke through binoculars. “Look at that.”

“Yes,” Zebari said, following his gaze. “Big hole.”

Between exercises, Iraqi officers assured U.S. officers that the demonstration was just a starting point for their modernizing forces, and U.S. officers assured Iraqi officers that they would receive their purchased equipment regardless of the “political decision” on the American training presence after Dec. 31.

This month, Baghdad requested that 5,000 or more U.S. military trainers remain, without immunity, a caveat that rules out the participation of American troops. In 2012, the Office of Security Cooperation-Iraq will employ just under 1,000 personnel to oversee the delivery and training related to foreign military sales.

Iraqi parliament members supporting the anti-American Shiite cleric Moqtada al-Sadr said Thursday that they will disrupt government activity if U.S forces remain in Iraq into 2012, according to the Reuters news service.

Special correspondents Asaad Majeed and Aziz Alwan in Kirkuk contributed to this report.