Mosul wasn't supposed to fall again. The city in Northern Iraq saw intense fighting between American forces and Saddam Hussein's sons in 2003, and in 2008 saw major campaign by American troops against insurgent forces. When ISIS attacked Mosul in summer 2014, two divisions of the Iraqi Security Forces were supposed to hold the city, but the 30,000 defenders crumbled and fled from the onslaught of under 2,000 enemies. Mosul remains in ISIS' hands today.

The fall of Mosul is as much about the security force's choice to retreat as it is about any tactical innovation by ISIS. Perhaps that's why, as Iraq's government continues its long slow war against ISIS, that they're looking to add a robot to the army.