BADANA PICHWK, Iraq — Kurdish forces on Monday morning began advancing on a string of villages east of Mosul, the start of a long-awaited campaign to reclaim Iraq’s second-largest city from the Islamic State, which seized it more than two years ago, officials said.
About 4,000 Kurdish pesh merga troops are involved in the operation to retake 10 villages, the opening phase of a battle that could take weeks or months and could involve nearly 30,000 Iraqi and Kurdish troops, with American warplanes providing air support. Iraqi counterterrorism forces, which work closely with American Special Operations commandos in Iraq, are also expected to join the Kurdish forces in the coming days.
The operation began hours after Prime Minister Haider al-Abadi announced in a brief speech aired on state television just before 2 a.m. that the long-awaited campaign to liberate Mosul had begun.
“The Iraqi flag will be raised in the middle of Mosul, and in each village and corner very soon,” Mr. Abadi said, dressed in a military uniform and surrounded by officers.
Defense Secretary Ashton B. Carter, in Washington, said the start of the Mosul campaign was a “decisive moment” in the effort to defeat the Islamic State.
In the first phase, the troops who have been massing at bases around Mosul in recent weeks will encircle the city, seeking to cut it off and prevent Islamic State fighters from fleeing, particularly west into Syria. Later, the counterterrorism forces, which took the lead in liberating other Iraqi cities, like Ramadi and Falluja, from the Islamic State, will join regular army units in storming the city.
After dark on Sunday evening, armored vehicles on flatbed trucks were seen moving west from Erbil, the capital of the autonomous Kurdish region, along with many ambulances.
The operation began under the light of the moon on Monday as pesh merga tanks, Humvees and pickup trucks with guns mounted on the back snaked their way toward the villages.
Although Mr. Abadi vowed that the Iraqi flag would be flown in every town, only the tricolor flag of the Kurdish semiautonomous region could be seen during the assault.
The Kurdish troops included the elite Zeravani paramilitary force, which attacked on three fronts. To avoid roadside bombs, a pesh merga column drove off the main highway, headed south on a rutted, undulating dirt road, and it then rumbled west across a dusty field.