Mike Giglio reports: ISIS is using improvised explosive devices, or IEDs, in staggering numbers across its fronts in Iraq. Experts say the weapon has never been used on this scale before — it is “unprecedented,” says Jonah Leff of the arms-tracking firm Conflict Armament Research, and “a revolution in their use and deployment.”

IEDs were the weapon of choice for Iraqi insurgents during the U.S. occupation — and their use by ISIS now is playing a crucial role as the war against them reaches a pivotal moment in Iraq. While U.S. warplanes pound the militants, they face multipronged assaults from local forces: the Kurds, Iraqi troops, and Iran-backed militia. New offensives countrywide have been billed as preludes to a battle for the northern city of Mosul, the prize of ISIS’s summer onslaught and the Iraqi heart of its self-styled caliphate.

The offensives span from Kirkuk in the north to the edge of Anbar province west of Baghdad and the city of Tikrit, where some 20,000 militia and Iraqi soldiers are engaged in the largest operation against ISIS to date. All have slowed amid the havoc wreaked by IEDs. Fighters from each of the forces battling ISIS say that — like U.S. troops before them — they suffer most of their casualties from the bombs. [Continue reading…]