The 94,000-member Iraqi-led coalition greatly outnumbers the 5-7,000 ISIS terrorists and has the benefit of air support from roughly 90 coalition and Iraqi planes. The force includes 54,000 members of the Iraqi Security Forces and 40,000 Kurdish Peshmerga fighters among which are 5,000 from other minorities including Christians, Turkmen and Yazidis.
ISIS deployed intense gunfire and suicide car bombers throughout Monday, while coalition forces advanced toward Mosul. ISIS attempted to drive suicide car bombs toward the leading Peshmerga convoy several times.
Kurdish Peshmerga forces cleared nine villages in an area measuring approximately 200 square kilometers. Forces east of Mosul also secured control over a significant stretch of the Erbil-Mosul road, a key strategic road.
Violence was limited at the villages on the city's outskirts but fierce resistance is expected from thousands of ISIS fighters in Mosul's urban center, including car bombs and improvised explosive devices.
The battle is expected to take months, but Iraqi forces have spent a year getting ready.
Before ISIS seized Mosul in June 2014, the oil-rich city had more than 2 million residents. Today, only 1 million residents remain. The cities of Ramadi, Tikrit and Falluja that had been captured by ISIS have already been reclaimed.
The Pentagon, which has lent advisers and air support, has earmarked about 500 of its nearly 5,000 service members in the country for the mission, including special operations forces among that number.
A humanitarian crisis is expected to loom in Mosul. The coalition airdropped leaflets told residents to tape up their windows, disconnect gas cylinders, and stay indoors out of fear they will be caught in sniper attacks, booby traps, crossfire and explosives.
The United Nations is building 22 sites to house an estimated 400,000 Iraqis fleeing the conflict in the early days of the battle.