BAQUBAH, IRAQ — The Iraqi government's most ambitious effort yet to assert its authority over long-troubled parts of the country began Tuesday with polite requests to search homes in and near this capital of Diyala province.
It was a modest and carefully prepared launch of a campaign that Iraqi commanders say will make use of nearly 30,000 Iraqi troops and eventually stretch across a region east of Baghdad that is roughly the size of Maryland. The government's previous crackdowns focused on individual cities.
"The mission is to clear the whole province . . . of terrorists and outlaws and to bring back security and stability," Lt. Gen. Ali Gaidan Najid, commander of the Iraqi ground forces, said at a meeting to coordinate operations with U.S. forces.
Iraqi soldiers and national police encountered no resistance as they knocked on doors in Baqubah and the town of Khan Bani Saad, about 15 miles south. But this is well-trod ground for the Iraqi forces and their U.S. counterparts, who have conducted repeated operations in the area since last year.
The troops will face a more serious test when they push into the province's hinterlands, where Sunni Arab militants loyal to insurgent groups including Al Qaeda in Iraq have found sanctuary since they were pushed out of the city of Fallouja, west of Baghdad in Anbar province, in 2004.
The U.S. military believes many insurgent leaders have already fled their hide-outs since Prime Minister Nouri Maliki announced at the end of June that he was sending reinforcements to Diyala. But they typically leave behind roads riddled with mines, houses rigged to explode and suicide bombers armed with explosives vests.
Diyala, an ethnically and religiously mixed region stretching from the eastern outskirts of Baghdad to the Iranian border, has long been a hotbed of violence. Al Qaeda in Iraq declared Baqubah the capital of its self-styled Islamic caliphate, and the group's founding leader, Abu Musab Zarqawi, died in a U.S. airstrike near the city in June 2006.
A series of U.S.-led campaigns, which began last year, restored a measure of calm to the main cities and towns along the central portion of the Diyala River, a region of rich farmland laced with canals that was long the breadbasket of Iraq.
But even with the extra forces deployed under the Bush administration's troop buildup last year, the American military did not have sufficient numbers to push into more remote parts of the province, where fighters hide among thick palm groves, and in isolated hamlets, vast desert expanses and rugged mountains. Most of the additional forces have returned home this year, and the U.S. presence in Diyala has dropped to less than half the level at its peak last summer.
U.S. commanders, who have also been ramping up operations in recent weeks, welcomed the deployment of additional Iraqi troops, who now outnumber them in the province about 5 to 1.
"I can't get out into the periphery without the additional Iraqi troops," said Lt. Col. Bryan Denny, acting commander of the U.S. Army's 2nd Stryker Cavalry Regiment, which assumed responsibility for security in the province in June. "I don't have the combat power to do that."
U.S. commanders, who had been expecting the Iraqi crackdown to begin later in the week, were caught off guard when hundreds of Iraqi troops cordoned off parts of the city before dawn Tuesday and began searching for weapons and fighters. But they quickly mobilized troops, which fell in behind the Iraqis in case they needed backup.
The U.S. officers' main concern was that the arrival of large numbers of predominantly Shiite Muslim troops to arrest Sunni Arab insurgents could trigger new clashes in a region scarred by years of sectarian bloodshed.
Residents too were apprehensive about the treatment they would receive, particularly members of the 10,000-strong local Sunni and Shiite guard force hired by the U.S. military to help ensure that insurgents do not return to their communities after major clearing operations are completed. Many members of the force are former insurgents now being paid by the Americans to keep order. Some worry they will be targeted by the Iraqi military for their past crimes.
In the days leading up to the crackdown, Denny urged Iraqi leaders to take into account the efforts of the so-called Sons of Iraq guards, who provide key information about insurgent networks and weapons caches.
"This could be the seminal event that fractures the province and pulls us back, or it could be the event that unites us," he said at a meeting at the provincial police chief's office. "What will make the difference is how they are treated, whether they all get their day in court."
Every detail of the Iraqi operation appeared to be aimed at allaying residents' fears -- down to its name, "Glad Tidings of Benevolence."