On the day the Islamic State overran the Iraqi city of Mosul in 2014, it laid claim to one of the greatest weapons bonanzas ever to fall to a terrorist group: a large metropolis dotted with military bases and garrisons stocked with guns, bombs, rockets and even battle tanks.
But the most fearsome weapon in Mosul on that day was never used by the terrorists. Only now is it becoming clear what happened to it.
Locked away in a storage room on a Mosul college campus were two caches of cobalt-60, a metallic substance with lethally high levels of radiation. When contained within the heavy shielding of a radiotherapy machine, cobalt-60 is used to kill cancer cells. In terrorists’ hands, it is the core ingredient of a “dirty bomb,” a weapon that could be used to spread radiation and panic.