Abstract: The Islamic State is the first non-state actor to have developed a banned chemical warfare agent and combined it with a projectile delivery system. However, it appears to have been forced to abandon its chemical weapons production after the loss of Mosul in June 2017. The absence of chemical attacks outside of Mosul after the city became cut-off from the rest of the ‘caliphate’ earlier this year indicates that the group has not established alternative production facilities. But U.S. intelligence believes that a new chemical weapons cell has been set up in the Euphrates River Valley.
In late July 2015, the Islamic State fired several mortar bombs at Kurdish People’s Protection Units (YPG) positions near the city of Hasakah in northeastern Syria. A statement released by the YPG after the attack described how the explosions had released “a yellow gas with a strong smell of onions,” and that “the ground immediately around the impact sites was stained with an olive-green liquid that turned to a golden yellow after exposure to sunshine.”1 Soldiers exposed to the substance reportedly suffered from nausea and burning sensations. U.S. officials later confirmed that samples taken from the site of the attack had tested positive for a small amount of mustard agent, in low concentration.2 This was not the first time the Islamic State or one of its predecessors had used chemicals as a weapon, but never before had a non-state actor developed the capability to combine production of a banned chemical warfare agent with a projectile delivery system.
The attack near Hasakah marked the culmination of nearly two decades of experimentation by Sunni jihadi groups, leading to the establishment of a dedicated chemical weapons (CW) program in the Iraqi city of Mosul, following the declaration of the Islamic State’s self-proclaimed ‘caliphate’ in June 2014. In the last three years, the Islamic State carried out attacks using chemicals on at least 76 occasions, according to IHS Markit’s Conflict Monitor open-source dataset. The graphic below (Figure 1) shows the distribution of these recorded events, which were gathered from a range of local news reports and social media.a
The Islamic State’s use of chemical agents in Iraq and Syria is characterized by three phases. During the initial phase, which encompasses the first year of the caliphate’s existence (between June 2014 and June 2015), chemical attacks drew on tried and tested techniques, adapted to include widely available industrial chemicals—mainly chlorine and phosphine—from stockpiles captured as part of the group’s territorial expansion. These attacks were carried out using crude delivery mechanisms, in most cases adding canisters of chemicals to roadside or vehicle-borne improvised explosive devices (IEDs). The second phase, from July 2015 to January 2017, represents the enhanced capability the group had achieved by combining the production of sulfur mustard agent with the means to deliver it using projectiles, such as mortar bombs and improvised rockets. During this period, chemical attacks were carried out simultaneously across the caliphate, from Syria’s Aleppo province in the west to Iraq’s Kirkuk province in the east, indicating the existence of multiple operational units with the required expertise. Attacks peaked in April 2016, with eight separate recorded chemical attacks in one month. The third phase began with the last recorded chemical attack in Syria on January 8, 2017, and ended with the Islamic State’s apparent abandonment of its CW production following the loss of Mosul in July 2017.
A History of Intent
The Islamic State’s CW program builds on nearly two decades of experimentation by other Sunni militant groups based out of Iraq. The Jordanian jihadi Abu Mus’ab al-Zarqawi showed an interest in developing CW as early as 1999. He initially established a jihadi training camp in Herat, Afghanistan, where his followers experimented with the production of toxins,3 but later moved this to Khurmul in northeastern Iraq after the U.S. invasion of Afghanistan in 2001. The Khurmul facility was captured by U.S. coalition forces in 2003, which reportedly found equipment and manuals for the production of CW, as well as traces of ricin and other poisons.4 In 2004, another laboratory linked to al-Zarqawi’s network was discovered in Fallujah, Anbar province, suggesting that the group had developed a rudimentary capability to build chemical IEDs.5 Other Sunni militant groups were experimenting with the use of CW at the same time. These include the al-Abud network, which also operated in the Fallujah area, and another unspecified group operating a laboratory discovered in Mosul, which contained more than 6,000 liters of chemicals.6
The most elaborate attempt to use chemicals in an attack during that period came in April 2004, when the Jordanian government announced it had thwarted a plot by al-Zarqawi’s network against the headquarters of the General Intelligence Directorate (GID) in Amman. The plot involved the intended use of three large trucks as vehicle-borne improvised explosive devices (VBIEDs) and up to 20 tons of mixed industrial chemicals. The mix of these chemicals was designed to enhance the explosive power of the IEDs and create a toxic cloud that would spread around the city, aimed at causing mass civilian casualties.7 Before his death in a U.S. airstrike in 2006, al-Zarqawi pledged allegiance to Usama bin Ladin, forming al-Qa`ida in Iraq (AQI), which later became the Islamic State of Iraq (ISI) and eventually formed the core of the Islamic State.
Al-Zarqawi’s network continued with the development of chemical IEDs and was widely assumed to be behind a series of chlorine VBIED attacks in Anbar province, beginning in October 2006.8 However, these had limited effect, as the containers designed for the safe transport and storage of chlorine were sub-optimal for its explosive dissemination by IED. The relatively low toxicity of the chemical was further decreased by the heat and blast pressure.9 In practice, the addition of chlorine did not increase the lethality of the IEDs beyond that of the conventional explosives. The psychological and political impact, however, attracted the attention of U.S. coalition forces, to track down and eliminate any individuals believed to be involved.10 The chlorine attacks stopped in 2007 after the arrest of a ‘key leader,’ believed to be Umar Wahdallah Dod al-Zangana,11 and no further reports of Sunni jihadis using chemicals emerged until June 2013, when Iraqi forces disrupted an ISI cell of five men who had set up three makeshift laboratories with the reported intent of manufacturing chemical agents and releasing them with remote-controlled helicopters.12
Expertise and Sourcing
Although the intent to develop a CW capability had existed for some time, it was the security of unchallenged territorial control, access to laboratory equipment in Mosul, and the relatively unrestricted availability of precursor chemicals—afforded by the establishment of the caliphate— which gave the Islamic State the opportunity to do so. Publicly available information on individuals killed or detained by the U.S. coalition in connection with CW suggests that the Islamic State assembled at least one dedicated team of technical experts to develop its CW program, using improvised laboratories hidden in Mosul’s residential neighborhoods to avoid U.S. coalition airstrikes.13 Available reporting suggests the group drew upon a combination of foreigners from Chechnya and Southeast Asia with relevant technical expertise who had migrated to the caliphate14 and those who had previously been involved in CW research for AQI and other Iraqi jihadi groups prior to the establishment of the Islamic State.15
Several Islamic State members killed or detained by U.S. forces for their involvement with CW in the last few years were reported to have been employed in Saddam Hussein’s CW program in the 1980s. One such individual, Abu Malik, who was killed in a coalition airstrike on January 24, 2015, was a chemical weapons engineer who worked at the Muthanna CW production facility before joining AQI in 2005.16 However, the level of expertise these individuals provided, and the importance of that expertise to the success of the Islamic State’s program, is sometimes overstated. None of the individuals reportedly killed or captured by the coalition were confirmed to have been senior members of Saddam’s program. The relatively low level of expertise demonstrated by the Islamic State suggests that those individuals recruited by the group, if they were in fact employed under Saddam, would likely have been lower-ranking members of the program.17 It is telling that no evidence has come to light publicly that the Islamic State has succeeded in producing more lethal chemical warfare agents, such as sarin or other nerve agents. The types of chemical agents used by the Islamic State, including low-grade mustard agent, do not require a high level of technical expertise to produce, and the knowledge is widely available.
There has been speculation over whether the Islamic State could have sourced CW from existing stockpiles belonging to the Iraqi or Syrian governments, both of which ran extensive CW programs in the past. The large number of CW munitions stockpiled in Iraq under Saddam Hussein and poor government documentation mean that many of these remained unaccounted for after the United Nations Special Commission’s (UNSCOM) process of reconciling the number of agents and weapons manufactured with what was consumed and remained. Even a one-percent margin of error would have resulted in thousands of abandoned or forgotten munitions.18 In fact, the CIA-led ‘Operation Avarice’ reportedly purchased 400 CW munitions between 2005 and 2006 that had found their way onto the black market.19 In Syria, interviews with army defectors suggest that some refused orders to deploy CW against civilians and buried their weapons stocks. For example, defected General Zahir al-Sakit claimed in an interview with Al Arabiya in 2013 that he had been ordered to use CW against the Syrian opposition near Houran in southwestern Syria, but he instead “ordered all chemical weapons to be buried.”20
During its period of rapid territorial gains in 2014, the Islamic State seized control of military sites where chemical munitions could have been hidden, abandoned, or lost. When the Islamic State took control of Saddam Hussein’s largest CW production and storage facility at Muthanna in July 2014, the U.S. Department of State acknowledged that a limited amount of CW precursors remained there.21 UNSCOM inspectors dismantled all CW production facilities and removed all equipment from Muthanna in the 1990s, with the exception of two bunkers, which were sealed by UNSCOM in 1994. Bunker 13 contained 2,500 sarin-filled 122mm artillery rockets, which were partially damaged or destroyed in a U.S. airstrike on the first night of the 1991 Gulf War. Leaking munitions, unstable propellant, and explosive charges made it too hazardous for U.N. inspectors to enter. Nearby, Bunker 41 was used to bury contaminated materials left over from the UNSCOM destruction program.22 When Iraqi forces regained control of the facility in late 2014, Iraq’s Deputy Foreign Minister Mohammad Jawad Al-Doraky stated that neither of the sealed bunkers had been penetrated by the Islamic State.23
The Organisation for the Prohibition of Chemical Weapons (OPCW) removed the last of Syria’s declared CW precursors and agents from the country in June 2014. But the lack of any overt process to verify the Syrian declaration led to speculation that Syria may have retained CW capability in some form, particularly compared with pre-declaration intelligence estimates.24 In May 2015, the Syrian local news channel All4Syria quoted a defecting army colonel, identified as ‘Ziad,’ who claimed that the government retained CW stocks at Sayqal Air Base, around 80 kilometers northeast of Damascus.25 When the same air base came under attack by the Islamic State in April 2016, government forces reportedly used sarin against them to avoid being overrun, according to a senior Israeli official quoted by The Telegraph newspaper.26
Although the Syrian government almost certainly retains stockpiles of CW,27 there is no evidence in the pattern of the Islamic State’s recorded use of chemical agents to suggest that the group acquired anything beyond rudimentary precursor chemicals. The precursors required for the production of chemical agents that have been used as weapons by the Islamic State, primarily chlorine and sulfur mustard, were, however, also available at industrial plants located in the territory of the caliphate. These include, for example, the Misraq chemical plant and sulfur mine, around 30 miles south of Mosul, which is believed to have held thousands of tons of sulfur and hydrogen sulfide,28 as well as numerous water treatment and fertilizer production plants, which tend to store large quantities of chlorine.29
Degradation of Capability
There were no recorded chemical attacks by the Islamic State in Iraq or Syria between June 2017, when it lost control of Mosul, and the time of writing in October 2017. Although there have previously been periods in which no chemical attacks were recorded for several weeks, a three-month break is unprecedented and is especially notable given that the group faced an existential threat to its core territory, including the city of Raqqa, during that time. The last chemical attack (at the time of writing) carried out by the Islamic State in Syria was on January 8 at Talla al-Maqri in Aleppo province. This compares with 13 such attacks in Syria over the previous six months, which were concentrated in the same area of Aleppo province. All other recorded attacks in 2017 were in Iraq, with 11 in Mosul and one near al-Atheem in Diyala province. The concentration of chemical attacks in Mosul after it had become cut-off from the rest of the caliphate in late 2016 suggests that the blockade on Mosul by Iraqi forces prevented the transfer of those weapons to Syria and that no further production sites were established elsewhere to compensate.
The Islamic State’s CW capability had already been significantly degraded before the loss of Mosul, as a result of U.S. coalition airstrikes against individuals and facilities associated with the program. A major breakthrough for the U.S. coalition came in February 2016, when U.S. Special Operations forces captured Suleiman Daoud al-Bakkar (aka Suleiman Daoud al-Afari) in Badoosh, a village north of Mosul. He was a leading figure in the group’s CW program and a reported former expert in chemical and biological weapons under Saddam. Al-Bakkar was interrogated for about a month and gave the United States unprecedented insight into the nature of the Islamic State’s program, including the names of key individuals and locations at which chemical agents were being produced and stored. The information led directly to a number of airstrikes against the program.30
The U.S. coalition’s success in disrupting the Islamic State’s CW program meant that the effort required to conceal and keep it running increased significantly in relation to the impact the weapons were having. In addition, the utility of CW on the battlefield is likely to have been displaced to some extent by the development of other weapons systems that achieved a similar psychological effect. In early 2017, the Islamic State began systematically using unmanned aerial vehicles (UAVs), primarily from the Phantom series of quadcopters produced by the private company DJI, to drop IEDs on enemy troop concentrations up to several kilometers behind the front line. In much the same way that the Islamic State used the release of chemical agents in Mosul to halt enemy advances by forcing them to take countermeasures, the presence of potentially armed UAVs had a similar impact. Due to the absence of reliable UAV countermeasures, Iraqi forces in most cases would be forced to take cover and engage the UAV with small arms fire.31 For the Islamic State’s UAV attacks, as for its chemical attacks, the psychological and harassing effect was far greater than the actual lethality of the weapons system, which did not exceed that of conventional indirect fire weapons. UAVs are cheaper and easier to use than chemical projectiles for that purpose, as the latter require specialist operators and equipment, which were in limited supply, and presented high value targets for U.S. coalition airstrikes.
Although the Islamic State appears to have abandoned the use of CW on the battlefield, it has most likely retained the aspiration, and at least the expertise, if not the equipment and precursor materials, to produce small batches of chlorine and low-grade sulfur mustard agent. Experts involved in the Islamic State’s CW program are likely to have been evacuated from Mosul to Syria alongside other senior members of the organization before it became isolated in late 2016. According to a U.S. official quoted by CNN in May 2017, the Islamic State was assembling a new chemical weapons cell in the Euphrates River Valley, somewhere between Mayadin and al-Qaim on the Syria-Iraq border.32 Although U.S. intelligence at the time assessed that the cell was seeking to consolidate its CW capabilities to support the defense of its remaining strongholds, that had not yet materialized at the time of writing.
As the remaining core of the Islamic State’s caliphate in the Euphrates River Valley comes under increased military pressure in late 2017, the group will be looking to transfer key figures, particularly individuals with high-value expertise—including in IED-making and the manufacture and use of CW—out of Iraq and Syria to other safe havens, most likely in Libya and the wider Sahel. This is likely to be enabled by the extensive people-smuggling networks that operate out of Kurdish-held territory in Iraq and the rebel-held Idlib pocket in Syria, bordering Turkey’s Hatay province.33
Threat to the West
There have been several Islamic State plots to carry out chemical terrorist attacks elsewhere, drawing on the expertise developed in Iraq and Syria. Australian authorities in Sydney disrupted a plot in July 2017 by two brothers, Khalid and Tarik Khayat, to deploy a device designed to release hydrogen sulfide, a toxic gas used briefly by the British Army, with limited effectiveness, as a chemical weapon in WW1.34 According to the Australian police, instructions on how to construct the device came from an Islamic State ‘controller’ in Syria. Military-grade explosives had been shipped to the pair with air freight via Turkey for a separate aborted plot to bomb a passenger jet. The brothers had also acquired in Australia some of the precursor chemicals for the poison gas plot, although they were reportedly “a mile and a half away” from constructing a viable chemical dispersal device.35 The plot illustrates how the Islamic State has the capability not only to transfer the know-how to produce toxic chemicals via secure online communications to operatives already living in target countries, but also to ship materials, including explosives, undetected.
Germany’s Federal Criminal Police Office (BKA) published a report in January 2017 highlighting the risk of chemical contamination of the water supply or food in grocery stores in Europe.36 The Islamic State has published English-language guides on its Wilayat Furat Telegram channel, such as the ‘Knights of the Lone Jihad’ series, which details how to do so by injecting groceries with cyanide poison or widely available pesticides, such as strychnine.37 However, most self-radicalized individuals carrying out attacks in the West have so far selected methods that are likely to result in their own death, or martyrdom, at the hands of the security forces. This partly explains the use of fake suicide belts and the combination of knife attacks with vehicle-impact attacks. The ‘anonymous’ poisoning of food and water supplies is likely to be a less attractive option for such individuals.
There is no publicly available evidence to suggest that the Islamic State has transferred sulfur mustard agent or other chemical weapons developed in Iraq and Syria to Europe. Although the Sydney plot demonstrates that the group has been able to ship explosives to a Western country undetected, it is far less likely that ready-made chemical weapons, such as sulfur mustard agent, could be shipped this way. The highly corrosive nature of such agents, and the highly controlled environments they must be stored in, mean that they are very difficult to transport over long distances without leaking.38 For that reason, the Islamic State would probably need to develop the agents shortly before they intend to deploy them, most likely in the target country.39
If the Islamic State were to organize a chemical attack in a Western city, the logistical challenges of transporting CW manufactured in Iraq and Syria and the generally low level of expertise the group has demonstrated suggest that an attack using widely available toxins or industrial chemicals would be far more likely than the use of blister or nerve agents like sulfur mustard or sarin. This significantly limits the potential lethality of such an attack. CTC
Columb Strack is a senior Middle East analyst with Jane’s by IHS Markit. He leads the company’s Conflict Monitor service, which provides data-driven insights and analysis into jihadi factions operating in Iraq and Syria.
[a] Given the nature of the source material, many of the reported incidents have not been independently verified.
 Nabih Bulos, “Islamic State confirmed to have used mustard gas against Kurds in Syria,” Telegraph, August 15, 2015.
 Barbara Starr, Jim Sciutto, and Elise Labott, “U.S. confirms ISIS used mustard agent,” CNN, August 14, 2015.
 Aaron Zelin, The War between ISIS and al-Qaeda for Supremacy of the Global Jihadist Movement (Washington, D.C.: The Washington Institute for Near East Policy, 2014), pp. 1-2.
 Jeffrey Fleishman, “Militants’ Crude Camp Casts Doubt on U.S. Claims,” Los Angeles Times, April 27, 2003.
 “Fallujah Update: Insurgent Chemical/Explosives Weapons Laboratory,” Combined Press Information Center, November 26, 2004.
 Ellen Knickmeyer, “Iraqi Chemical Stash Uncovered,” Washington Post, August 14, 2005.
 John Vause, Henry Schuster and David Ensor, “Jordan says major al Qaeda plot disrupted,” CNN, April 26, 2004.
 Jim Garamone, “Terrorists Using Chlorine Car Bombs to Intimidate Iraqis,” American Forces Press Service, June 6, 2007.
 Karl Dewey, “Evolution of Islamic State CW capability,” Conflict Monitor by IHS Markit, February 2016.
 Peter Bergen, “Reevaluating Al-Qa’ida’s Weapons of Mass Destruction Capabilities,” CTC Sentinel 3:9 (2010): p. 2.
 “Jane’s CBRN Assessments – Proliferation – Iraq,” Jane’s by IHS Markit, August 14, 2017.
 David Blair, “Iraq arrests five in ‘al-Qaeda chemical weapons plot,’” Telegraph, June 2, 2013.
 Hiwa Ahmed, “IS Tests Chemical Weapons on Prisoners,” Basnews, May 23, 2016.
 Hamza Hendawi, Qassim Abdul-Zahra, and Ken Dilanian, “Officials: Islamic State seeking chemical weapons,” Times of Israel, November 19, 2015.
 Kyle Orton, “The Islamic State and Chemical Weapons,” The Syrian Intifada blog, September 30, 2016.
 “ISIL Chemical Weapons Expert Killed in Coalition Airstrike,” CENTCOM, January 30, 2015.
 C.J. Chivers and Eric Schmitt, “C.I.A. Is Said to Have Bought and Destroyed Iraqi Chemical Weapons,” New York Times, February 15, 2015.
 “Syrian army ordered to use chemical weapons, defected general tells Al Arabiya,” Al Arabiya, April 28, 2013.
 Damien McElroy, “ISIS storms Saddam-era chemical weapons complex in Iraq,” Telegraph, June 19, 2014.
 “Iraqi army retakes chemical weapons site from Islamic State,” Reuters, December 1, 2014.
 Mohammad Anas, “Da’ish sets its sight on al-Sin military airbase and the regime prepares to leave it,” All4Syria, May 29, 2015.
 David Blair, “Assad’s forces have ‘used sarin nerve gas’ for the first time since Syria’s notorious 2013 massacre,” Telegraph, May 17, 2016.
 Rebecca Collard, “UN blames Syrian government for chemical attacks,” Financial Times, September 6, 2017.
 Josie Ensor, “Isil rig chemical plant with explosives after launching first mustard gas attack on US troops since WWI,” Telegraph, September 22, 2016.
 Helene Cooper and Eric Schmitt, “ISIS Detainee’s Information Led to 2 U.S. Airstrikes, Officials Say,” New York Times, March 9, 2016.
 Author interview, Mitch Utterback, journalist, February 2017.
 Ryan Browne and Barbara Starr, “First on CNN: ISIS creating chemical weapons cell in new de facto capital, US official says,” CNN, May 17, 2017.
 “Borderless: Undercover with the People Smugglers,” Al Jazeera, May 12, 2016.
 Charles Howard Foulkes, “Gas!” The story of the special brigade (Uckfield, U.K.: Naval & Military Press, 2001), p. 105.
 Paul Maley, “From Syria to Sydney: how the airport terror plot unfolded,” Australian, August 5, 2017; “AFP and NSWP Discuss the Two Sydney Men Charged over Alleged Terrorist Acts,” Australian Federal Police National Media press conference, August 4, 2017.
 “Die Regierung warnt vor Terror mit Chemikalien,” N24, January 24, 2017.
 “IS supporters distribute English message suggesting to poison food in markets,” Site Intelligence Group, September 3, 2017.
 Stephen Hummel, “The Islamic State and WMD: Assessing the Future Threat,” CTC Sentinel 9:1 (2016): pp. 18-21.