daesh tunnels, west mosul / by Maranie Staab

a hole that isis members once used to travel through west mosul, from house to house, on foot, relatively undetected (by aircraft and soldiers as they were out of the streets) is seen patched up. local residents shared stories of daesh putting holes in the walls of their homes and it becoming "normal" to be sitting inside and to have fighters run through. 
the group is known for their use of ieds and passageways, both among the reasons that the fight against isis has and continues to be unlike most other conflicts.