Peshmerga forces belonging to the Iraqi Kurdish Regional Government on the move near Mosul on Tuesday. Photograph: Anadolu Agency/Getty Images
The battle to retake Mosul is the greatest challenge Iraqi forces have faced, the British defence secretary has said, warning that Islamic State fighters were unlikely to be ousted quickly.
Michael Fallon said there were likely to be extensive causalities during the intense operation against Isis, which could last several months. “We recognise, as do the Iraqis, that this will be the greatest challenge that their security forces have yet encountered, with significant humanitarian implications,” he told the Commons.
Fallon said it was clear that the Iraqi army, the Kurdish peshmerga and coalition forces would recapture the city, which has been occupied since 2014. “This will not be a quick operation, and we can expect Daesh [Isis] to fight hard to keep Mosul,” Fallon said.
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No compatible source was found for this video. Kurdish peshmerga sprint through fierce gunfire during Mosul offensive
“When I visited Baghdad and Erbil three weeks ago, senior Iraqi and coalition commanders outlined their plans for Mosul. Their confidence is high and it is clear that Daesh is now failing.”
Isis forces once claimed swaths of Iraqi territory but a number of serious defeats mean they now hold only 10% of the ground in Iraq, Fallon said. “As we enter the third year of the campaign, real progress is being made and defeating Daesh in the long term will help make the streets of Britain and Europe safer.”
Fallon said the RAF was assisting with intelligence-gathering and intensive air support. British military experts are also providing support and training to Iraqi forces.
Barack Obama also warned on Tuesday that results in Mosul should not be expected quickly, saying it would be a “difficult fight”. The battle to remove IS from the main Iraqi stronghold “will be another step toward their ultimate destruction,” the US president told reporters at the White House.
After months of preparation the Iraqi government launched the operation to take back the city on Monday, its largest since the 2011 withdrawal of US troops.
The government’s 30,000 troops are also joined by fighters from both local Sunni groups and Iranian-backed Shia militias, forces which have previously been rivals, as well as the Kurdish peshmerga forces pushing the eastern assault of the city.
Aid groups have warned of a potential humanitarian crisis, with Isis likely to use residents as human shields, shooting on sight anyone attempting to flee. Both the Red Cross and the International Organisation for Migration have also raised fears that Isis may be prepared to use chemical weapons.