Mosul: The ugly, deadly urban warfare facing Iraq's elite troops

Iraq's counter-terrorism forces admit that the mission to retake Mosul could take months

The fight to retake the city of Mosul has barely begun, and militants loyal to so-called Islamic State (IS) have shown that they will not be leaving quietly.

Snipers, car bombs and booby traps were awaiting the Iraqi elite counter-terrorism forces on Tuesday as they approached the city from the east.

The men of the CTF, as the special forces are known in Iraq, appear casual - but make no mistake, they are ready.

Many have scars from Ramadi or Falluja - or both. They have lost friends. Some are younger than you might expect for the fighting they have experienced.

Many are also recently married - it is common practice before deploying for battle - and they are keen to show pictures of their new brides on their smart phones.

• Battle for Mosul: The story so far

• Video: Moment troops enter the city

• IS and the crisis in maps

From low-ranked soldiers to top generals, two things are repeated with sincerity when talking to the CTF; this is not going to be an easy fight. The mission could take months.

But liberating Mosul is the fight they have been waiting for. They see the city as a bastion of hatred, a place where a poisoned cloud formed before it blew across their country.

That has nothing to do, however, with how they view the massive civilian population of Mosul.

The CTF have to contend with snipers, car bombs and booby traps as they approach Mosul

Arguably, nobody better understands what life has been like for civilians living under IS rule than the CTF, who are often the first to enter occupied areas.

A Humvee gunner, who is known as "The Bullet", has been shot and is riddled with shrapnel after fighting in other parts of Iraq over the past year.

We show each other pictures of our families and he tells me he only has two "loves" - his wife and his country.

His smile does not give away all that he has done and seen.

His friend, another gunner, shows me pictures of tortured bodies that the pair had come across in Falluja.

One commander is Major Salam - he has a full name, but here, he doesn't need it. His men follow him without question and he is known as a "door-kicker".

He is always in front of his men; his body is visibly riddled with proof of his "lead by example" mantra. He spent weeks in France this year for medical reasons, after fighting in Falluja.

If there are unsung heroes in their ranks, it is the men driving the bulldozers. They are sent in quickly to destroy the wildly complicated network of tunnels that IS has been using for over two years to avoid air strikes from the US-led coalition.

The tunnels are often rigged with powerful explosives, set up as the enemy retreats further into the heart of the city.

Urban warfare - ugly, confusing and deadly - awaits the CTF and thousands of other Iraqi forces in Mosul.

Nobody thinks a genuine victory will be easy or bloodless.