Iraqi armed forces are moving to retake western Mosul from ISIS.
Planes dropped millions of leaflets over the western half of the city, urging fighters to surrender and asking citizens to hang a white flag outside their home.
The United Nations estimates up to 800,000 people are still living in western Mosul.
The effort to liberate Mosul, at one time Iraq's second-largest city, began in October. The terrorist group was kicked out of the eastern half of the city by January.
Taking control of the western half of the city will likely be more difficult. The buildings are tightly packed, and small alleys could make it harder for military vehicles to get through. And the western half of the city is more densely populated.
ISIS took control of Mosul in 2014. It remains their last major stronghold in the country.