A once great metropolis, Mosul is the final stronghold for the so-called IS caliphate in Iraq.
As Iraqi forces rally to the south and the Peshmerga holds a ring to the east of the city,.
According to Ash Collingburn, visiting fellow at the Australian Strategic Policy Institute and commanding officer of Australia's first training team tasked with skilling up the Iraqi forces in 2015, it will be weeks before the forces can even reach the city.
Map and graphic about the battle for Mosul Source: AFP
The population of Mosul was more than two million before IS moved in. Now it's somewhere between one and one and half million.
"I don't think anybody knows exactly," Mr Collingburn said.
Iraqi forces are stationed at the Qayyarah base 70km south of the city - equivalent to the trip between Adelaide and the retirement hot spot of Victor Harbor. The Peshmerga are keeping their line approximately 20km east of Mosul, similar to the distance between Adelaide and Mount Barker in the Adelaide Hills.
"The current battle plan sees anti-IS forces assemble to the north, to the south and to the east of Mosul," he said.
Map of Adelaide highlighting Mount Barker and Victor Harbor Source: Carto / OpenStreetMap
"What the battle plan does is leave the west open so that Islamic State fighters can withdraw from the city.
"If I could take that and use Adelaide as the example here - if you could imagine surrounding Adelaide from all of those directions and to the west you've got the water."
"They will use drones and the like to surveil that approach for IS fighters fleeing. The rationale is that it’s easier to destroy them in the open than it is in the urban environment."
By car, a trip from Mount Barker in Adelaide's Hills down into the city takes half an hour along the South-East Freeway. The approach to Mosul is likely to take weeks.
Mr Collingburn believes the major roads into Mosul will be avoided due to the dangers left by IS fighters. He predicts extremely slow progress from the liberating forces as they approach the city over rough terrain infested with traps designed to inflict maximum damage.
SBS spoke exclusively to Mr Collingburn, whose experience with the Australian military in Iraq goes back to 2007, about how he sees the situation play out.
Why Mosul is important
Iraqi and Coalition forces have forced IS fighters back into a block of territory stretching across Syria and northern Iraq.
Within this area are two major cities: Mosul and the Syrian city of Raqqa, 400km to the west.
"Further shrinkage of their so-called caliphate really means that the caliphate is starting to lose its legitimacy," Mr Collingburn said.
“It will lose the attractiveness for foreign fighters and their message of this so called invincible caliphate.
"They really are now on the back foot."
but several thousand fighters remain defending the city.
"The interesting thing to watch will be to what the actions of IS,” Mr Collingburn said.
"Are they going to stay and fight to the last man or are they going to try to move some of their fighting force out back into eastern Syria to preserve their force for another day."
What fighting in the city will be like
Once the liberating forces reach the city, they face multiple threats from IS.
"We know [IS has] extensive tunnelling throughout Mosul so they can get around without exposing themselves in the city,” Mr Collingburn said.
"They have already been using suicide bombers and oil fires to obscure their positions and their movement from the air."
One of the gravest threats is presented by networks of bombs and mines known as complex improvised explosive device belts.
"In the city they will rig them up and it's not just one house detonating, it's a series of houses detonating,” Mr Collingburn said.
What Australia is doing
Australian troops have taught the Iraqi army many of the skills that will assist them as they advance towards the city.
Mr Collingburn said the training Australia has provided has been focused on “obstacle breaching” to navigate the many traps, mines and snags that await the liberating force.
“(We have been) teaching them how to use their engineering, armour and infantry to break these obstacle belts which then gives them the ability to use that corridor,” he said.
Australian planes will also provide air support from a base in the United Arab Emirates to the south.
Vehicles lined up for an attack on Mosul. Source: Sputnik International
Mr Collingburn suggested equipment like mine detectors and even robots may be used, but he was reluctant to go into detail for fear the Iraqi forces’ capabilities could become known to IS.
What will happen to the city
Mr Collingburn describes the military challenge to oust IS from Mosul as “really tough”, but he believes that may not be the most complex part of the Middle East operations.
“(The battle for Mosul) is definitely the biggest challenge that they have faced yet, but perhaps the military part of this isn't the most complex,” he says.
“If the political issues aren’t dealt with - if they don't shore up the peace - the conditions will be set in the future for another insurgency.
"If it’s not the Islamic State, it’s going to be something by another name."
What will happen to the refugees
The UNHCR predicts up to 750,000 people will flee Mosul, creating a massive humanitarian crisis as winter approaches, when temperatures at night can fall to -12 degrees Celsius.
UNHCR has prepared three camps offering protection and aid for 150,000 people fleeing Mosul.
It is currently preparing aid and equipment which includes 11,600 tents and 88,235 heating stoves and is calling for donations.
There are already 3.3 million Iraqi refugees being supported by UNHCR as a result of the war against IS.
