The long-awaited offensive to retake Mosul from the Islamic State group began Monday with a volley of U.S.-led coalition airstrikes and heavy artillery bombardments on a cluster of villages along the edge of Iraq's historic Nineveh plain east of the militant-held city.
Iraq's Kurdish peshmerga fighters led the initial assault, advancing slowly across open fields littered with booby-trapped explosives as plumes of black and orange smoke rose overhead -- the opening phase of an unprecedented campaign expected to take weeks if not months, and involve more than 25,000 troops.
By the end of the day Kurdish forces had retaken some 200 square kilometers (80 square miles), according to the president of Iraq's Kurdistan region. Peshmerga commanders on the ground estimated the offensive retook nine villages and pushed the frontline with IS back eight kilometers (five miles).
But the forces' hold appeared fragile and the gains largely symbolic. Some of the villages were so small they comprised no more than a few dozen homes, and most were abandoned.
And though some troops were less than 30 kilometers (20 miles) from Mosul's edges, it was unclear how long it would take to reach the city itself, where more than 1 million people still live. Aid groups have warned of a mass exodus of civilians that could overwhelm refugee camps.
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Iraq's second-largest city, Mosul fell to IS in the summer of 2014 as the militants swept over much of the country's north and central areas. Weeks later the head of the extremist group, Abu Bakr al-Baghdadi, announced the formation of a self-styled caliphate in Iraq and Syria from the pulpit of a Mosul mosque.
If successful, the liberation of the city would be the biggest blow yet to the Islamic State group. After a string of victories by Iraqi ground forces over the past year, IS now controls less than half the territory it once held, and Iraqi Prime Minister Haider Al-Abadi has pledged the fight for Mosul will lead to the liberation of all Iraqi territory from the militants this year.
Al-Abadi announced the start of the operation on state television before dawn Monday, launching the country's toughest battle since American troops withdrew from Iraq nearly five years ago.
"These forces that are liberating you today, they have one goal in Mosul, which is to get rid of Daesh and to secure your dignity," al-Abadi said, addressing the city's residents and using the Arabic acronym for IS. "God willing, we shall win."
In Washington, Defense Secretary Ash Carter called the Mosul operation "a decisive moment in the campaign" to defeat IS. The U.S. is providing airstrikes, training and logistical support, but insists Iraqis are leading the campaign. On Monday, Pentagon press secretary Peter Cook said a small number of U.S. troops were serving as advisers to Iraqi and peshmerga forces on the outskirts of Mosul.
More than 25,000 Iraqi and Kurdish troops will be involved in the operation, launching assaults from five directions, according to Iraqi Brig. Gen. Haider Fadhil. The troops include elite Iraqi special forces who are expected to lead the charge into the city, as well as the Kurdish forces, Sunni tribal fighters, federal police and state-sanctioned Shiite militias.
In a political deal between the country's Kurdish region and the central government, it was agreed that Kurdish forces would advance first, bringing the villages they retake under their regional control, according to Iraqi special forces Lt. Col. Ali Hussein.
Once the Kurdish forces advance far enough, the Iraqi special forces will move to the new front and pick up the fight.
Speaking at a news conference just a few kilometers (miles) from the frontline, the Kurdistan region's President Massoud Barzani called the Mosul operation a "turning point in the war against terrorism," but said there was not yet a plan for governing the region after the fight. Political and military officials in the Kurdistan region have previously said the peshmerga will not withdraw from any territory they retake.
Saud Masoud, a soldier with Iraq's special forces watched the frontline on the horizon Monday while waiting for orders to advance. Originally from the Christian village of Bartella, the outskirts of which were obscured by plumes of smoke, he said he personally didn't want his hometown to become part of the country's Kurdistan region, but he understood why Iraqi leaders struck the deal.
"People are tired of the situation, very tired honestly, so everyone including myself is willing to compromise," he said.
As airstrikes and heavy artillery pounded the squat, dusty buildings, the area -- historically home to religious minorities brutally oppressed by IS -- was almost completely empty of civilians, thus allowing air power to do much of the heavy lifting.
Lt. Col. Mohammad Darwish said the main roads and fields were littered with homemade bombs and that suicide car bomb attacks slowed progress.
Fighters entered the villages in Humvees but did not get out of their vehicles because it was too dangerous, a Peshmerga major said, speaking on condition of anonymity as he was not authorized to brief the press.
The IS-run news agency, Aamaq, said the group carried out eight suicide attacks against Kurdish forces and destroyed two Humvees belonging to the Kurdish forces and Shiite militias east of the city.
Kurdish forces confirmed at least one such attack. Hisham Kazar, a Kurdish peshmerga fighter said one of his relatives died Monday as the Mosul operation got underway when a suicide car bomber rammed the Humvee he was riding in.
"This kind of sacrifice is worth it because we are fighting for Kurdish territory," he said, "I wouldn't say the same if we were fighting in Iraqi land."
The operation so far hasn't run into what is expected to be one of its most significant obstacles: Mosul's civilian population of more than a million people. The United Nations said Monday that the largest wave of displaced people is expected to begin next week as Iraqi forces enter territory where thousands are living.
The political and security crisis triggered by the fall of Mosul more than two years ago also contributed to the rise in power of armed groups that only loosely fall under the control of the central government. Some Iraqi politicians have warned that even after a victory in Mosul, violence could erupt between groups who once had a common enemy.
The role of Shiite militia forces in the Mosul operation has been particularly sensitive as the groups have been accused of carrying out abuses against civilians in other mostly Sunni parts of Iraq where they have operated.
At a frontline some 30 kilometers southeast of Mosul, Kurdish peshmerga fighter Sarwat Faris, dressed in a black commando uniform, prepared to roll into a village held by IS. He said he believes pushing the militants out of Mosul will make Iraq's north safer, but he doesn't believe it will bring peace to the country as a whole.
"Next, the fight will be between us and the (Shiite) militias," he said. "They don't like us because we are Kurdish and Sunni, they hate our people, and we hate them."
"Maybe as soon as the New Year, we will be fighting each other."
Associated Press writers Adam Schreck in Irbil, Iraq; Ahmed Sami and Sinan Salaheddin in Baghdad; Qassim Abdul-Zahra in Khazer, Iraq; Maamoun Youssef in Cairo; Geir Moulson in Berlin; Suzan Fraser in Ankara, Turkey, and Vivian Salama in Washington contributed to this report.