52,000 extra troops deployed in surge for West Mosul

The fresh push in the four-month operation to retake Mosul involves federal police forces, as well as elite units under the supervision of the interior ministry, army soldiers and Hashd al-Shaabi (Popular Mobilisation) paramilitary fighters. 

"The federal police has resumed its advance... Our cannons are targeting [IS] defence lines with heavy fire," federal police chief Raed Shaker Jawdat said in a statement.

An extra 52,000 fighters have been brought into the battle against IS, a source from the Joint Special Operations Command in Baghdad confirmed to The New Arab.

The renewed offensive - which began on Sunday night - saw Iraqi forces push northwards towards the city's airport.

The assault marks a new phase in the broad operation launched on October 17 to retake Mosul, Iraq's second city and the militants' last major stronghold in the country.

More than 46,000 former residents of the eastern half of the city, divided north-south by the River Tigris, have returned to their homes following the routing of IS fighters on that side in recent months.

The western side of the city, however, is home to the labyrinthine old city, with narrow streets and vast potential for insurgent fighting, ambushing and booby-traps.

There are an estimated 750,000 civilians also trapped there with dwindling food supplies.

On Sunday, Save the Children said that all parties should protect the estimated 350,000 children among them.

"This is the grim choice for children in western Mosul right now: bombs, crossfire and hunger if they stay - or execution and snipers if they try to run," said the charity's Iraq director, Maurizio Crivallero.

The recapture of Mosul would deal a death blow to IS' self-proclaimed "caliphate". Territory under the extremist group's control has been shrinking for two years with the advance of a global anti-IS coalition.

But IS has put up stiffer resistance than expected in some areas, including its Mosul stronghold.

This is the grim choice for children in western Mosul right now: bombs, crossfire and hunger if they stay - or execution and snipers if they try to run Maurizio Crivallero, Iraq director, Save The Children

It took Iraq's most seasoned elite Counter-Terrorism Service two months to retake the east of the city, and commanders and experts believe the city's west bank could prove even harder to retake, with the narrow streets of the Old City forcing Iraqi forces to undertake perilous dismounted raids.

IS is also "likely has stronger support within western Mosul, and the ISF (Iraqi security forces) are more likely to encounter populations that are wary or hostile," said Patrick Martin, an Iraq analyst at the Institute for the Study of War in comment to AFP.

Yet after a lull in the four-month operation, optimism is high on the front lines.

"I don't expect a very difficult fight: their end has arrived," Hakem Gassem Mohammed, an officer with the interior ministry's Rapid Response force told an AFP reporter south of Mosul.

The first day of the rekindled offensive saw forces advance in sparsely populated areas just south of the city itself.

Elite units trained for urban warfare are expected to move into west Mosul at a later stage.

On Sunday, Iraqi forces retook 15 villages on three different fronts converging towards the airport, according to a top army commander coordinating the operation, Abdulamir Yarallah.

Meanwhile, militants defending Mosul's west bank have no choice but to defend their bastion as escape routes remain cut off and bridges across the Tigris in the city lay destroyed.

More than half a million residents remained in their homes when Iraqi forces entered east Mosul to battle IS there, leading to a smaller displacement than initially feared.

But figures working in humanitarian relief have said the assault on west Mosul could cause a bigger exodus.

"We are racing against the clock to prepare emergency sites south of Mosul to receive displaced families," the UN's humanitarian coordinator in Iraq, Lise Grande, said in a statement.