It doesn’t look like an improvised explosive device—at least, not the stereotypical kind. This one, from a part of northern Syria that ISIS used to control, looks more like a high-school science project volcano. Covered with a little dirt and some leaves, it’d probably pass for a rock, until someone tripped the hidden trigger and detonated the fragmentation device hidden inside.

But the trickiest part of the bombs ISIS has left behind, across thousands of square miles of Iraq and Syria, isn’t just their looks. "The coverage area appears to be huge swaths of the territory and growing all the time. The density is high, as well" says Ed Rowe, a program manager for Norwegian People's Aid, a humanitarian group putting together an IED clearance and risk education program in Iraq. "The level of sophistication seems to be increasing, and they’re definitely targeting the clearance teams."

IEDs aren't a new weapon for ISIS. In fact, the group is still using some of the same designs its predecessors used during the US occupation of Iraq. But ISIS's IEDs are causing unique problems for those tasked with clearing them because of both the unprecedented scale of production and the fact that it's using the weapons in different ways, and against different targets.

New Bombs

During the Iraq occupation, the Islamic State of Iraq and al-Qaeda used improvised bombs to, among other things, target coalition vehicles along roads and highways. But as the Assad regime's grip on Syria crumbled, ISIS gained territory and strength, controlling a caliphate that stretched from Syria almost to the outskirts of Baghdad. With thousands of square miles to defend, ISIS began using IEDs like traditional landmines, planting them underground in large, densely-packed defensive swathes outside important population centers to seal residents in and keep enemies out.

"They have the same role as a conventional landmine, except they contain much more explosive and can be activated over a larger area of ground," Rowe says.

The demand for mass production led to greater standardization of designs and components. Even today, as the caliphate crumbles, Norwegian People's Aid is seeing a new IED design, complete with machined firing pins and a fuse derived from commercial equipment.

IED charges. Fulmer estimates the metal containers towards the front could contain up to 100kg of explosives. ROJ MINE CONTROL Organızatıon

ISIS has also been known to add booby-traps within IEDs to target explosive ordnance disposal teams trying to disarm them. Even if only a small percentage of the weapons are outfitted to kill EOD personnel, clearance teams still have to treat every device as a potential trap. "You have to treat every item you see as if it’s an IED until you prove it’s not, so that necessarily makes the pace of work go a lot slower," says Jerry Guilbert, deputy director for programs at the US State Department’s Office of Weapons Removal and Abatement.

WIRED showed images of IEDs taken by the ROJ Mine Control Organization, one of the groups trying to deal with the problem, to Kenton Fulmer, an explosives expert at Armament Research and Johns Hopkins University. Fulmer says they’re similar to IEDs he saw with the military in Mosul in 2008. “The sealant is a design signature,” he says; ISIS’ predecessor organizations sometimes used sealant to keep moisture out of their devices.

"The caliphate, it has essentially a weapons program. IEDs are standardized to a high degree," Fulmer says.

In urban areas, the terrorist group uses a different, often more complex kind of IED. They’re more like booby traps themselves, designed to explode when someone picks up a blanket or opens a door. That’s what Janus Global Operations, a State Dept. contractor, is reporting in schools and buildings in Iraq*. "A lot of the items that Janus is finding in urban areas were planted specifically to target civilians," Guilbert says.

A Cleanup Problem

Getting rid of IEDs isn't simple, even for organizations that work in the dicey business of removing explosives from the battlefields. The humanitarian groups often charged with clearing explosive ordnance aren't used to working with IEDs. Traditional mine action operations have focused on removing mines produced by established arms companies with well-known disposal procedures. Skilled personnel can teach those to locals in a matter of weeks. IEDs, however, require personnel with harder-to-find and more expensive skills, like military veterans.

ROJ MINE CONTROL Organızatıon

In Iraq today, dealing with leftover IEDs is relatively easier—the country has a functioning government. Humanitarian groups, the United Nations Mine Action Service, and non-governmental organizations funded by the State Department can coordinate with Iraqi government's mine action agencies.

But in northern Syria, where the American-backed Syrian Democratic Forces have pushed ISIS out of a handful areas, the landscape of IED cleanup is less clear. In Syria's Al-Hasakah governorate, RMCO and its team of roughly 30 people has been working on its own, without help from international humanitarian groups or the US-backed anti-ISIS coalition. But Col. John Dorrian, a spokesperson for the US-led coalition, says that the US provides training on the IED threat at the unit and staff level to allies, including an IED awareness course and basic equipment.

Teaching local forces how to dispose of explosives can be a delicate issue, though. The military sometimes holds back on teaching select techniques. "Everyone's really testy when you learn about how to take an IED apart safely, because that goes hand-in-hand with learning how to build an IED. It also goes hand-in-hand with how to kill people who are taking apart IEDs," says Fulmer. "As an EOD tech, I don't want lots of people knowing how to kill me while I work."

Many more people will have to learn that trade, though. In Syria and Iraq, an empire of explosives still reigns in hidden underground and urban caches. Disposal teams and civilians will be fighting the last vestiges of the caliphate long after it collapses.

*UPDATE 11/22/16 9:51 AM This story originally misstated the country where Janus Global Operations is dealing with IEDs on contract with the US State Department.