Camp Sykes, Iraq ? Nearly a year ago, U.S. forces swarmed through Tal Afar, killing enough insurgents for the local police chief to declare the city insurgent-free. Now the militants are back, and the United States has moved in more soldiers to drive them out.

The story of Tal Afar, an ethnically diverse city located near Camp Sykes and about 40 miles from the Syrian border, underscores the gamble Washington will be making by turning over large areas of the country to Iraqi control so U.S. soldiers can begin going home next year.

When the insurgents were driven from Tal Afar, the United States scaled back. But the small number of U.S. soldiers remaining – along with the new Iraqi soldiers – were unable to prevent the insurgents from returning.

“The enemy had sensed a reduction of U.S. forces,” said Col. H.R. McMaster, commander of the 3rd Armored Cavalry Regiment, which was rushed here from Baghdad, 260 miles to the southeast, earlier this year.

Now McMaster’s regiment – which oversees Tal Afar as well as more than 185 miles of Syrian border – is trying to uproot insurgents who have averaged over 150 attacks per month, an exceptionally high rate for a city of some 200,000 people.

After U.S. forces crushed the insurgents in Tal Afar last fall, only about 500 American soldiers were left to guard the city, which was mostly in the hands of the Iraqis. But the insurgent ranks swelled, allowing them to control entire neighborhoods.

At the time, the Syrian border was manned by Iraqi guards whom American soldiers privately considered either corrupt or incompetent.

Insurgents cheer and make gestures of victory signs in Tal Afar, northern Iraq, in this Sept. 5, 2004, file photo. Nearly a year ago, U.S. forces swarmed the city of Tal Afar, killing enough insurgents for the local police chief to declare the town insurgent-free. Now the insurgents are back, and the U.S. command has moved more U.S. soldiers here to drive them out.

In June, the 3rd Armored Cavalry launched an offensive in Tal Afar. Now American officers say they are seeing slow progress, including the recent capture of key insurgent financiers, McMaster said. In addition, more than 250 suspected insurgents were recently arrested.

“We’ve taken away the enemy’s main strengths: their ability to hide in the population,” McMaster said.

Tal Afar is strategically important to both the insurgency and the U.S. military. As the closest major city to the northern border with Syria, it serves a way station for foreign insurgents sneaking into Iraq, officials say.

Hundreds of U.S. troops recently were sent to the border to try to curb the infiltration.

Tal Afar’s troubles stem in part from tensions among its diverse ethnic groups – Turkomen, Kurds and Arabs. Turkomen, a national minority with Turkish roots, form the majority in the city. But the Turkomen community is split between Sunni and Shiite factions.

Those tensions were heightened by a power struggle after the collapse of Saddam Hussein’s regime in 2003; the population was left feuding among itself.