Late this spring, Iraqi forces fighting ISISin Mosul discovered three unfired rocket-propelled grenades with an unusual feature — a heavy liquid sloshing inside their warheads. Tests later found that the warheads contained a crude blister agent resembling sulfur mustard, a banned chemical weapon intended to burn a victim’s skin and respiratory tract. The improvised chemical rockets were the latest in a procession of weapons developed by ISIS during a jihadist arms-manufacturing spree without recent analog. Irregular fighting forces, with limited access to global arms markets, routinely manufacture their own weapons. But ISIS took the practice to new levels, with outputs “unlike anything we’ve ever seen” from a nonstate force, said Solomon H. Black, a State Department official who tracks and analyzes weapons. Humanitarian de-miners, former military explosive ordnance disposal technicians and arms analysts working in areas captured from ISIS provided The New York Times with dozens of reports and scores of photographs and drawings detailing weapons that the militant organization has developed since 2014, when it established a self-declared caliphate in Syria and Iraq. The records show the work of a jihadist hive mind — a system of armaments production that combined research and development, mass production and organized distribution to amplify the militant organization’s endurance and power. One report noted that before being expelled from Ramadi, ISIS fighters buried a massive explosive charge under a group of homes and wired it to the electrical system in one of the buildings. The houses were thought to be safe. But when a family returned and connected a generator, their home was blown apart in an enormous blast, according to Snoor Tofiq, national operations manager for Norwegian People’s Aid, which is clearing improvised weapons from areas that ISIS left. The entire family, he said, was killed. Craig McInally, also an operations manager for the Norwegian demining organization, described indiscriminate inventions elsewhere — including four seemingly abandoned space heaters and a generator recovered near Mosul. The heaters and generator, useful to displaced civilians and combatants alike, were packed with hidden explosives. The bombs had been configured, Mr. McInally said, so that if a person approached them or tried to move them, they would explode. Taken together, the scope and scale of ISIS production demonstrated the perils of a determined militant organization allowed to pursue its ambitions in a large, ungoverned space. Some weapon components, for example, were essentially standardized, including locally manufactured injection-molded munition fuzes, shoulder-fired rockets, mortar ammunition, modular bomb parts and plastic-bodied land mines that underwent generations of upgrades. Many were produced in industrial quantities. The findings also included apparent prototypes of weapons that either were not selected for mass production or were abandoned in development, including projectiles loaded with caustic soda and shoulder-fired rockets containing blister agent. While ISIS has been routed from almost all its territory in Iraq and Syria, security officials say that its advances pose risks elsewhere, as its members move on to other countries, its foreign members return home and veterans of its arms-production network pool and share knowledge and techniques online. “They’re spreading this knowledge all over the world,” said Ernest Barajas Jr., a former Marine explosive ordnance disposal technician who has worked with ordnance-clearing organizations in areas occupied by ISIS. “It’s going to the Philippines, it’s in Africa.” He added, “This stuff’s going to continue to grow.” Born of Insurgency One reason for ISIS level of sophistication was clear: Its armaments programs grew out of the insurgencies fighting the American occupation of Iraq from 2003 through 2011. Sunni and Shiite militant groups became adept at making improvised bombs, both from conventional munitions abandoned in 2003 by Iraq’s defeated military, and with ingredients that bomb-makers prepared themselves. American officials say certain Shiite groups received technical assistance and components from Iran. Sunni bomb makers also fielded chemical weapons, sometimes by combining explosive devices with chlorine, a toxic substance with legal applications, and other times in bombs made from degraded chemical rockets or shells left from Iraq’s defunct chemical warfare program. ISIS, which evolved from Al Qaeda in Iraq, built upon its predecessors’ lethal industry. The group’s larger success since also played a role. When ISIS seized swaths of territory and major cities in 2014, it took control of shops and factories with hydraulic presses, forges, computer-driven machine tools and plastic injection-molding machines. It also moved into at least one technical college and university lab. This infrastructure positioned ISIS for an arms-production breakout. Behind the capacity was an armaments bureaucracy that supervised product development and manufacture, said Damien Spleeters, head of operations in Iraq and Syria for Conflict Armament Research, a private arms-monitoring and investigative firm that has done field work in both countries during the war. The system was resilient, Mr. Spleeters said. One of ISIS projects, a series of recoilless launchers that gained prominence late in the battle for Mosul, in northern Iraq, was built from the ground up even while militants were pressured in combat from multiple foes on multiple fronts. “It just kept going,” Mr. Spleeters said of the technical advancements. “They could develop stuff even as they lost territories.”The New York Times)