Portals were generally constructed into the walls and floors of houses, which were derelict by the time Kurdish forces took the city. Various media sources quote Kurdish commander Shamo Eado as claiming: "Daesh dug these trenches in order to hide from air strikes and have free movement underground as well as to store weapons and explosives. This was their military arsenal.
"As we clear the city of explosives, we expect to find more tunnels. It is just a matter of time."
