Iraqi and Kurdish forces backed by U.S.-led airstrikes advanced on Mosul on Monday, as part of a long-awaited operation to retake Iraq's second largest city from the Islamic State group.
The unprecedented operation is expected to take weeks, even months. Though some of the forces are less than 30 kilometers (20 miles) from Mosul's edges, it was not clear how long it will take to reach the city itself. Once there, they have to fight their way into an urban environment where more than 1 million people still live.
Aid groups have warned of a mass exodus of civilians that could overwhelm refugee camps.
Iraqi Prime Minister Haider al-Abadi announced the start of the operations on state television, launching the country's toughest battle since American troops withdrew from Iraq nearly five years ago.
Mosul, Iraq's second largest city, 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 Mosul would be the biggest blow yet to the Islamic State group. Al-Abadi pledged the fight for the city would lead to the liberation of all Iraqi territory from the militants this year.
With AP files
Michael Knights, a fellow of The Washington Institute for Near East Policy, specializing in the military and security affairs of Iraq, Iran, and the Persian Gulf states. He recently wrote about how to secure Mosul for the think tank
Judith Yaphe, an adjunct professor at the Institute for Middle East Studies at The George Washington University. She specializes in Middle Eastern political analysis