A military operation led by Iraqi forces was launched today aimed at ending ISIS' control of Mosul, Iraq.
The city, which has been under ISIS rule for two years, is the group's last major stronghold in the country.
US military officials estimate there are 3,500-5,000 ISIS fighters in Mosul. ISIS supporters say there are at least 7,000 fighters there.
Some Peshmerga commanders who are part of the offensive expect it will take at least three months to clear the city as ISIS may leave sleeper cells behind. Others expect a quicker victory, with ISIS leaders choosing to retreat to the vast desert west of Mosul.