The battle to liberate Mosul

Smoke billows in the Iraqi city of Nineveh during an operation against Islamic State in an image captured from the top of Mount Zardak, about 15 miles east of Mosul.

Iraqi Kurdish Peshmerga fighters atop Mount Zardak. Islamic State seized Mosul, once the country’s second-largest city with a diverse population of about 1.2 million, in 2014.

Iraqi Kurdish Peshmerga fighters fire a multiple-rocket launcher from Mount Zardak. Officials dropped leaflets on Mosul in recent weeks urging residents to shelter in place once the offensive started.

Iraqi forces head north toward Mosul on Monday, part of the operation to retake the city from Islamic State.

Iraqi forces in Shourah prepare to advance toward Mosul on Monday.

Iraqi policemen clean a weapon at the Qayyarah military base, south of Mosul, on Sunday.

Iraqi forces gather at the Qayyarah military base, about 35 miles south of Mosul, on Sunday.

Iraqi Kurdish Peshmerga fighters fire a mortar shell from Mount Zardak.

Iraqi Kurdish Peshmerga fighters atop Mount Zardak on Monday.