In a televised statement Monday morning, Iraqi Prime Minister Haider al-Abadi said "the victory bell has rung" in the massive mission to retake the historic city and free roughly 1 million residents from the "brutality and terrorism of ISIS."
If that happens, the Abadi government would claim a major victory after struggling to boost its credibility, prove its military prowess and end the terrorist group's territorial dominance in Iraq's oil-rich north.
Throughout the past year, the coalition has prepped for the major offensive against ISIS—one that started with targeted airstrikes by US-led coalition and Iraqi forces.
But for Mosul to be recaptured, not only must a diverse coalition of Iraqi, Kurdish and American forces defeat ISIS fighters, they must do so while following the lead of Iraqi forces. In a country filled with no shortage of factions, that's easier said than done.
The last stand for Mosul
After ISIS claiming considerable territory in Iraq in its attempt establish an Islamic caliphate, Iraqi forces have driven its fighters out of much of the country including the cities of Tikrit, Ramadi and Falluja.
Mosul, a city almost 3,000 years old, represents ISIS' last stand in Iraq. Before becoming ISIS' top prize in the Iraq, Mosul was inhabited by more than 2 million people. Only about 1 million residents remain today.
The fight for Mosul is expected to last weeks—potentially months–and if the battles to wrest Falluja and Ramadi from ISIS' grip are indicators, Mosul will be a messy melee.
Last Friday Abadi visited oil-rich Kirkuk province ahead of the operation to liberate the city of Hawija after it fell under ISIS control in 2014. After nearly clearing ISIS from Anbar and Salaheddin provinces, retaking Hawija would be strategic as it would reduce the threat to Iraqi and Peshmerga forces who would have their backs to the city during the battle for Mosul.
Iraqi forces march toward Mosul
More than 54,000 Iraqi troops are now tasked with recapturing Mosul, according to Lt. Gen. Stephen Townsend, commander of Combined Joint Task Force Operation Inherent Resolve.
The coalition comprises many groups, but is mostly made up of Iraqi and Kurdish Peshmerga fighters. According to Abadi, the official offensive plan calls for only forces with the Iraqi army and National Police will enter the city
"No others," Abadi said.
The Iraqi-led forces also include the Popular Mobilization Units, largely Shiite paramilitary forces with Sunnis and Christian fighters, had planned to target ISIS tunnels and trenches south of Mosul with thermobaric missiles.
In addition, thousands of Kurdish forces have dug in from other directions in the desert outside Mosul. East of the city near Khazir, Kurdish troops have closed in with their armored vehicles. As Peshmerga and ISIS forces exchange fire, CNN's Nick Paton Walsh has heard airstrikes from above coming from coalition planes.
"I've just seen a loud airstrike go in right in front of us here," CNN's Nick Paton Walsh said. "That kind of explosive power only happens from some kind of a coalition device."
The Pentagon, which has lent advisers and air support, recently announced the deployment of 600 additional American troops to aid in the Mosul's capture, bring the number of US personnel to more than 5,200.
Fight could last "many months"
Ahead of the assault, as leaflets proclaiming "it's victory time" rained over the city Sunday, skirmishes flared outside Mosul in advance of the Iraqi campaign.
US military officials estimate there are up to 5,000 ISIS fighters in Mosul. ISIS supporters put the number at 7,000.
ISIS militants have taken measures to combat the effectiveness of airstrikes. Plumes of black smoke rose from oil-filled trenches on fire outside northeastern Mosul, an attempt by ISIS to obscure its fighters' positions during airstrikes, military sources said.
Even still, though, one airstrike hit one of Mosul's main bridges, a precursor to the potential conflict coming to the city.
On ISIS' side, there have been reports of a growing network of tunnels leaving the city. A tunnel network large enough to accommodate motorbikes stretches from the outskirts of the city to the nearby village of Hamdania, according to the source.
The terrorist outfit has also allowed wounded fighters to leave Mosul for Raqqa, Syria, the group's de facto capital, a source inside Mosul said. At checkpoints, ISIS fighters wore masks to disguise their identities in what is seen as a sign of decreasing confidence, as well as concerns about retaliation from Mosul residents.
ISIS have started to free prisoners who were jailed for low-level offenses related to their beards, cigarettes or clothing, the source added.
Others, however, expect a quicker victory with ISIS leaders.
What happens next?
As Iraqi-led forces approach the city, Mosul's remaining residents still remain in the clutches of an organization known for exploiting civilians as human shields.
Camps are being set up to accommodate the refugees, who will need transport and basic necessities once the Iraqi security forces and Peshmerga screen them as they leave the city.
"The humanitarian consequences of this operation will be massive," said Wolfgang Gressmann Norwegian Refugee Council's Country Director in Iraq. "Establishing genuinely safe routes out of the city for civilians is now the top priority; nothing is more important."
Diplomats and Kurdish officials have already expressed concerns about who would stabilize and govern Mosul for those who chose to stay. According to US Deputy Secretary of State Antony Blinken, a holding force of about 15,000 Sunni elements was being trained and equipped to secure the city once it's liberated.
"There are no major objectives after that," Navy Capt. Jeff Davis, a Pentagon spokesman, said. "This is it."
CNN's Arwa Damon, Ben Wedeman, Hamdi Alkhshali, Daniel Nikbakht, Susanna Capelouto, Nick Paton Walsh, Ghazi Balkiz and Mohammed Tawfeeq contributed to this report.