Are Iraqi-led forces close to victory, or are the militants digging in for a lengthy and dogged war of attrition?
Mosul is ISIS's last major stronghold in Iraq -- and the terror group has shown that it is willing to go to almost any lengths to keep hold of it, using everything from suicide bombs to booby-trapped toys
in its desperate fight.
ISIS has had months to prepare
for the offensive -- building tunnels, constructing explosives, rigging abandoned houses to detonate and plotting counterattacks; reinforcements were reportedly brought in from Raqqa in Syria to help defend the city.
The conflict is "not a conventional war,"
according to Iraq's former foreign minister, Hoshyar Zebari.
And even as areas are swept clean of ISIS fighters, the battle is not over: It will take months to clear the terrorists' former territory of IEDs.
"They put them on the road, in the houses. We liberate a village and they are everywhere -- people come back to their homes, open a door or even a refrigerator and it blows up," says Brig. Gen. Bajat Mzuri of Zeravani Special Forces.
An estimated 100,000 troops, including Iraqi soldiers, Peshmerga fighters, Sunni tribal paramilitaries and Christian and Turkmen militias are involved in the offensive, though not all are on the front line. Hundreds of airstrikes have been carried out by the US and others in support of the coalition.
Iraqi-led forces entered Mosul on November 3
, after more than two weeks fighting their way across the plains to the east of the city, through nearby towns and suburbs
And in recent days, the Hashd al Shaabi paramilitary forces have recaptured a key airbase near Tal Afar, 70 kilometers (43 miles) west of Mosul.
But it has not all been good news.
Inside Mosul, the coalition is meeting fierce resistance, and an ISIS counterattack on the Mosul suburb of al Zahraa, a week after it was recaptured, left at least two dead.
An audio message, purportedly from ISIS leader Abu Bakr al-Baghdadi, has been credited with emboldening the group's fighters
, and inspiring them to keep up their resistance.
Peshmerga spokesman Brig. Gen. Halgurd Hikmet told CNN this week that "for ISIS, Mosul is survival
" -- they will not give the city up easily.
Along with their gains, coalition fighters have made countless grim discoveries, including mass graves
, bodies stuffed into wells
and others hanging from lampposts
, all attesting to ISIS's brutal resolve.
Those who stayed
When ISIS took control of Mosul in 2014, about half of the city's 2 million residents fled, but many stayed on, afraid of leaving their homes for an uncertain future.
As the offensive began, human rights groups and NGOs warned that 1.2 million Iraqis in the region were in "grave danger" as ISIS and the coalition faced off.
Hundreds of people living in ISIS-controlled villages outside Mosul were rounded up and taken into the city
to be used as human shields as Iraqi troops and Peshmerga closed in.
The Iraqi Security Forces have used radio broadcasts and leaflets airdropped into the city
to urge civilians to stay where they are.
Others are simply too scared to leave -- dozens of civilians have been killed, either deliberately targeted by militants, accused of collaboration with the ISF or caught in the crossfire.
Save the Children estimates that 600,000 children remain trapped inside Mosul; boys as young as 9 are being kidnapped
by ISIS and forced to fight on the terror group's behalf, according to the United Nations.
In outlying villages where ISIS forces have been routed, citizens celebrated their liberation by shaving off their beards
and smoking -- things banned while their homes were under ISIS control.
Those who escaped
The UN's Office for the Coordination of Humanitarian Affairs (OCHA) says 59,000 people have been displaced since the start of the Mosul offensive
They have made perilous journeys to get out of the city and the surrounding towns and villages, leaving them doubly traumatized.
"Many children have been through two years of ISIS and were then forced to flee through a war zone," said Aram Shakaram, the NGO's deputy country director for Iraq. "Some told us they have seen people shot and hanged. Imagine what effect that would have on a child."
Three quarters of those who have fled since the battle began are now in temporary camps in Nineveh, Irbil and Anbar provinces, having left everything behind
A few have been lucky enough to return to their homes -- Asa'ad and his family were forced to join 600 families on an ISIS march
from their home in Tulul al Nasir. They managed to escape, but many of their friends and neighbors are still missing.
What happens next?
The fight for Mosul is unlikely to reach a swift conclusion. The coming weeks -- or even months -- are likely to see ISF troops dragged into ongoing urban combat, ridding the city of ISIS fighters street by street -- it will be slow going.
Slower still will be efforts to clear the booby traps and bombs they've left behind.
Meanwhile, as the tide turns against them, key members of the terror group will likely flee to ISIS's Syrian heartland, in and around Raqqa.
And once the city is fully liberated, another fight will begin: to repair the damage caused by the terror group.
How you can help
Thousands of civilians have fled Mosul as troops move in to liberate the city from ISIS. Click here to support some of the groups on the ground in Iraq
helping displaced families.