Iraqi troops, backed by U.S.-led coalition forces, are pushing deeper into Mosul in their offensive to drive out ISIS from the country’s second-largest city. Soldiers from Iraq’s emergency response division are reportedly close to storming the city’s old quarter. Observers say this could lead to an ISIS counter-offensive. The Iraqi push to re-take Mosul comes as some ISIS fighters are having second thoughts about what they are fighting for. Holly Williams reports from the frontlines.