Since October 2016, Iraqi forces have been battling to recapture the city of Mosul from ISIS militants, who had overrun it in just a few days two years previously. With nowhere to run, ISIS dug in for a long and gritty fight, using car bombs, snipers, mortars and IEDs to block the troops advance. Unable to flee, for fear of being executed by ISIS, most of the 400,000 people still thought to be trapped in the shrinking caliphate, hid in their basements as the fighting raged on above them. At the time of writing, the troops had reached the edge of the old part of the city, taking heavy casualties as they recaptured territory from the militants, one house at a time.