Abstract: With the July 2017 Sydney hydrogen sulfide plot, there is some evidence that the Islamic State has transferred its chemical warfare (CW) expertise from the battlefield to its foreign terrorism activities. Despite this development, Islamic State appears to put scant organizational stock into the use of CW to advance its strategic goals. Though this lack of enthusiasm cannot be confirmed without secret intelligence or broad primary source data, the Islamic State’s most obvious means of threatening CW attacks—its affiliated propaganda organs—appear to lack any mention of CW events, prowess, or alleged planning. Ultimately, the Islamic State CW experiment seems to predict little about the future of the group’s chemical terrorism.
During the Islamic State’s brief control of territory in Iraq and Syria, its forces repeatedly employed chemicals in both offensive and defensive operations.a In the absence of access to appropriate sources, whether human or documents, it is difficult to draw firm conclusions about the Islamic State’s desire to acquire and use chemical weapons. Furthermore, the question remains as to why the Islamic State did not extend this capability into its far-reaching foreign terrorism campaign. Indeed, there is open source evidence of only one instance in which the Islamic State directed the transfer of chemical warfare (CW) related skills to its al-Amn al-Khariji (External Operations) operatives or their remote associates.b Moreover, Islamic State CW activities in theater were possibly relegated to a “special operations” unit—known as “Jaysh al-Khalifa” or “Jaysh Dabiq”—which may have been responsible for all CW deployments in Syria and Iraq.1 c Considering these notions, available evidence reveals no trends concerning the Islamic State’s present and future chemical terrorism ambitions. The more critical question becomes: can the Islamic State’s CW experimentation reveal anything about future chemical terrorism threats? This article will argue it cannot.
The Islamic State’s Use of Chemical Weapons
The Islamic State has demonstrated a willingness to use any means to maximize the harm and disruption it inflicts upon its enemies. Starting in 2014, these means came to include chemical weapons, which were utilized in possibly 37 discrete attacks in Syria and Iraq,d causing a handful of confirmed deaths and a limited number of injuries.e
In the course of its operations, the Islamic State has utilized two basic classes of agents: weaponized toxic industrial chemicals (TICs) and warfare agents. The use of weaponized TICs, dominated by the use of chlorine, illustrated the Islamic State’s willingness, and capacity, to effectively adapt resources that came into its hands. It also clearly demonstrated that the group had no compunctions about adopting CW. Chlorine was deployed frequently between August 2014 and June 2015 but slowed to a trickle thereafter. In total, there were at least 20 strongly supported instances of the use of chlorine by the Islamic State.f In addition, there are indications that Islamic State forces may have used chlorine grenades and other small-scale delivery methods extensively in the course of their defense of Mosul and other sites in north-central Iraq, although these attacks have not been recorded in detail.2 A noteworthy feature of these deployments is that they all occurred in Iraq.
In addition to chlorine, the Islamic State appears to have employed other TICs on an experimental or opportunistic basis. Phosphine, an organophosphorus compound commonly used as an agricultural fumigant, was allegedly used in a series of attacks in the vicinity of Hasakah, Syria, on June 28, 2015.3 Islamic State forces reportedly used vinyltrichlorosilane, a compound used in the production of plastic and rubber products,g in at least one attack,4 although this agent’s use is not strongly supported, with only two sources of doubtful reliability mentioning it.5
In a grave development, the Islamic State also made use of the CW agent sulphur mustard. The initial deployments of mustard agent occurred in August and September 2015. A second set of attacks took place in February and March 2016.h Significantly, it appears that this agent was actually produced by the group, which would make it only the second violent non-state actor (VNSA) to have produced warfare agents in any useful quantity.i Although there was a suspicion that the Islamic State had simply deployed agent taken from Saddam-era stockpiles, analysis of samples gathered at the site of the August 21, 2015, attack in Marea, Syria, clearly refuted this. The analysis revealed that the agent employed had been produced using the Levinstein method6 rather than the Meyer-Clarke method used in the Saddam-era program,7 strongly supporting the contention that the agent was self-produced.
The Islamic State’s CW activities have been almost entirely confined to battlefields and their immediate environs, using a variety of artillery and mortar systems for agent delivery. Otherwise, the Islamic State’s CW use seemed designed to slow enemy advances through the extensive use of roadside bombs. The Islamic State’s CW approach is markedly different to that adopted by its precursor organization, al-Qa`ida in Iraq (AQI). AQI carried out an explicit chemical terrorism campaign between October 2006 and June 2007.8 All told, AQI conducted approximately 20 attacks using vehicle-borne improvised explosive devices (VBIEDs) charged with varying quantities of chlorine gas.9 These attacks struck residences, marketplaces, and other public gathering areas, and in one attack, U.S. military personnel, northeast of Baghdad.10 AQI demonstrated a capacity to refine its methods with early attacks “poorly executed, burning the [chlorine] rather than dispersing it”11 whereas in March 2007, AQI coordinated two to three massive chemical attacks in Fallujah and Ramadi, exposing as many as 300 civilians in a single incident.12 Not long after this successful operation, the campaign ceased.j In contrast to AQI’s progression, there was no apparent evolution in the generally unsophisticated delivery systems employed by the Islamic State.
As for the broader reaches of the putative caliphate, there are apparently no open source reports of a single chemical IED among the scores of devices the Islamic State has used in other theaters or terrorist operations.k It is true that jihadis do not differentiate between “terrorist” and “tactical” applications, preferring to see all such operations as “military” in nature. This all-inclusive approach raises questions about why the Islamic State has largely refrained from employing CW abroad in pursuit of the strategic goals it associates with terrorism.
Propagandizing or Not
One rich vein of data on Islamic State activities comes from its own propaganda—less so the famously slick Dabiq and Rumiyah, more so the battlefield chronicler, al-Naba.13 The toll of the Islamic State’s far-flung operations, as well as its Syria and Iraq actions, can be read in the weekly’s pages. As part of an effort to assess potential chemical terrorism pathways last year, the authors surveyed over 80 issues of the above titles.l The absence of any mention of chemical agents or allusions to chemical capabilities in any of the issues published within a week or less of some 16 chemical incidents is quite surprising.m
The Islamic State’s use of chemical weapons on the battlefield overlapped mere tactical objectives. For example, at Taza Khurmatu, Iraq, in March 2016, chlorine and mustard agent were mixed in with artillery barrages targeting areas just beyond the battlefield proper, exposing civilians and combatants in rear areas and along likely supply routes.n The Islamic State’s understanding of CW’s potential use to generate panic amongst local enemies connects to the fact that the organization considers psychological warfare, terrorism, and tactical combat as part and parcel of the same operational doctrines. The Islamic State’s choice to employ CW agents, as it did, suggests that a link between the group’s operational calculus and its strategic objectives may have had some initial traction in its leaders’ minds.
It is difficult to perfectly substantiate the Islamic State’s knowledge of Iraqis’ fear of chemical weapons, but circumstantial evidence is abundant. A British CW expert who has had extensive contact with Iraqi, Syrian, and Turkish medical and military professionals reports that many of these individuals profess to a dread of “gas” and basic misunderstandings of the nature of various CW agents for preparedness and defense purposes.14 In Iraq, this dread is predicated on the Saddam-era use of chemical weapons for internal suppression. On a number of occasions, Iraqi political figures have dismissed or denied the very existence of Islamic State CW capabilities, likely in the hope of allaying civilian fears.15 For example, Hakim al-Zamili, chairman of the Iraqi parliament’s security and defense committee, alleged in 2016 that the notion was an American fiction and that claims that the Islamic State’s CW specialist, Suleiman Dawoud al-Afari, had been captured were baseless.16 Islamic State propagandists are likely to have been aware of these official statements and their motivation.
Since Aum Shinrikyo’s spectacular mid-1990s attacks, the West has manifested a growing and somewhat sensational fear of chemical terrorism—as potentially threatened by the Islamic State itself against Europe, if not the United States—reflected in both official analyses and news reports.17 Whether one believes that the media drives public perceptions or that media aligns to the public’s thought life, Islamic State propagandists may have easily read this trend themselves. John Cantlie, a British journalist forced into Islamic State propaganda services after late 2012, either chose to exploit or was ordered to stoke Western fears of nuclear terrorism in Dabiq #9.18 In that issue, the feature article implies that the Islamic State was well aware of European and American psychological vulnerabilities related to CBRN.19
Certainly the linkages between Islamic State propagandists and the organization’s leadership are imperfectly understood. But considering that the group’s propaganda was most likely intended to hype “statehood” through the boasting of state-level technical prowess, and, more critically, to draw followers into its fold or convoke them to homespun violence, Islamic State propagandists saw fit to talk up even the most ambiguously successful operations. Why then omit such an obvious accomplishment as the CW program? Could the effort have been too important or too unsatisfying to propagandize? Did Islamic State insiders quickly begin to consider the program ineffective or non-strategic by nature? Might they have feared moral outrage from their supporters or cadres? Again, the exact answers are unclear but to believe that the Islamic State neglected this opportunity without good motive is very difficult.
The clarion contrast between the Islamic State’s lack of propaganda output on CW and its regular media celebration of even the smallest tactical activities, and the determination to demonstrate technological achievements as seen with the adoption and publication of advances in the employment of drones as weapons, suggests Islamic State leadership did not unambiguously support the CW effort. There are several reasons why this might be the case, including the possibility that the effort was a low priority, pet project of a limited number of actors within the organization.
The Islamic State’s leadership, and the organization more generally, is likely to have learned a number of lessons from the CW effort. First, the organization (and at least some of its members) is likely to have an enhanced understanding of the difficulties of producing, weaponizing, handling, and effectively deploying CW agents. Secondly, the organization may, based on results from field deployments, have concluded that CW agents are ineffective tools for generating significant numbers of casualties, which may affect any consideration of future use of these agents in terrorist operations.o To date, there is only one indication that the skills and training required to weaponize chemicals (or produce CW agents) have been transferred out of the Syria-Iraq theater.p While it is possible that some survivors of the units involved with the production and use of chemical agents have escaped from the territory of the former caliphate, only the Sydney hydrogen sulfide plot offers any suggestions about what Islamic State chemical terrorism may actually entail.
Certainly, the New South Wales Police discovery of hydrogen sulfide precursors in the possession of aspiring Islamic State allies could seem to indicate a strategic evolution toward chemical attacks. But this single data point may speak more to the tactical improvisation of the Islamic State handler who directed the plot from afar.q When the Khayat brothers failed to get an IED onboard a passenger flight in July 2017, the handler probably instructed them to quickly set up a fake powder coating company and begin experiments in TIC weaponization and dispersal.r Hydrogen sulfide is among the less difficult substances to produce outside of an industrial setting, but poses impressive risks to the layman and furthermore to successful lethal deployments.20 Switching from an IED to this particular chemical may have been driven more by a newly chosen target or by the prerogative of the handler.s More confounding to a connection between Islamic State strategy and the Sydney plot is the status of the remote controller. If an al-Amn al-Khariji coordinator, as is plausible, then his personal initiative to option a TIC would not necessarily have needed a superior’s review or approval, though this does not eliminate leadership involvement.t New details may change this assessment, but the Sydney chemical plot seems best understood as a context-specific innovation instead of an organizational trend.u
Be that as it may, the Islamic State’s use of CW is primarily of interest for its illustration of the potential for quasi-state organizations with territorial control to employ military capabilities typically associated with state military forces. In the case of the Islamic State, the adoption of chemical weapons is clearly unusual when compared to other insurgencies with territorial pretensions or active control throughout the MENA region and throughout history more generally. It is likely, though difficult to prove, that the Islamic State’s employment of chemical weapons was very much a product of the circumstances of the group’s rise. This surely helps to explain both the Islamic State’s interest in developing CW capabilities as well as perhaps why those capabilities have not been applied outside Iraq and Syria. Iraq, after all, has a long history of production and use of chemical weapons, which is likely to have ensured the availability of the necessary technical personnel, awareness of the associated technologies, and its probable utility in theater. In addition, the extensive use of chemical weapons by the Syrian government since late 2012 is likely to have been a further factor in attracting attention to chemical weapons and commercially available TICs.v
While the Islamic State has demonstrated on multiple occasions an essentially unrestrained willingness to engage in attacks on civilian populations, its CW activities show a tight association with battlefield tactics. As such, although the Islamic State’s CW activities undoubtedly represent an interesting data point, not least in terms of the scientific and engineering capacity of insurgencies, and its ability to address the challenges of production and weaponization of CW agents, that data point does not tell us much of anything useful about how the Islamic State or a successor organization might seek to employ chemical weapons against remote Western targets. It may, however, be relevant for those planning future operations against insurgencies with territorial control in so far as it suggests the need to consider that insurgents may employ chemical weapons against Western forces or their local proxies.
This does not diminish the fact that terrorist organizations or their operatives may come to fetishize chemical and other warfare agents because of the fear they can induce, much as Aum Shinrikyo did. However, given the Islamic State’s limited chemical warfare activities, the concern generated by these deeds does not yet justify seeing the Islamic State as an inevitable chemical terrorism danger. And though Western security agencies are correct to monitor this threat vector, publicized warnings remain alarmist for the time being. CTC
Markus Binder, Jillian Quigley, and Herbert Tinsley are staff researchers at the Unconventional Weapons and Technology Division (UWT) within the University of Maryland’s National Consortium for the Study of Terrorism and Responses to Terrorism (START). This article arose from their Department of Homeland Security-funded work on an Islamic State chemical and biological weapons behavioral profile, which analyzes the group’s potential CB attack modalities against U.S. and Western interests. Questions can be addressed to htinsley [at] umd [dot] edu.
[a] This article’s findings are based on research conducted by the authors as part of a predictive analysis of potential Islamic State chemical terrorism pathways against the United States and its allies and interests. The work was funded by the Department of Homeland Security and the report furnished to the funding office. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security or START. All information contained in this article is solely derived from open sources and represents the authors’ integrative opinions on what the research offered which is of pertinence to the broader question here posed.
[b] That exception is the July 2017 plot allegedly involving Australian brothers Khaled and Mahmoud Khayat. An individual identified by the Australian Federal Police as a senior Islamic State figure in Syria instructed the Khayats in constructing a device that could disperse hydrogen sulfide, a toxic industrial chemical. See “AFP (Australian Federal Police) and NSWP (New South Wales Police) discuss the two Sydney men charged over terrorist acts,” AFP on Periscope, August 3, 2017. The Sydney Morning Herald alleges a public transit target for the chemical device. See Rachel Olding, “Khaled Merhi pleads not guilty to weapons charge after Sydney ‘bomb plot’ raid,” Sydney Morning Herald, August 24, 2017. This development followed a failed attempt to down an Emirati airliner using an improvised explosive device. While some aspects of this plot are still unclear, the authors discuss the pertinent implications toward the end of this article.
[c] This certainly does not rule out other Islamic State assets with chemical weapons expertise or experience. Most importantly, there does appear to have been a group responsible for CW testing and development, which U.S. military efforts seem to have degraded by the summer of 2016.
[d] This figure, and all other data unless otherwise cited, is from the authors’ open source research and is included in the report referenced in footnote a. The exact number of attacks is difficult to pin down. Many have likely gone unreported, whether in local news reports or in the international media. The authors compiled incident data from three different sources in order to focus their research efforts. However, of those that were indicated, some have been disproven, some reports retracted, and still others were documented on the basis of dubious open source evidence. The authors have come to the conclusion that the majority of available data on Islamic State chemical weapons incidents is non-authoritative, particularly in the cases of chlorine and other weaponized industrial chemicals. Generally speaking, reports on mustard agent attacks are better supported due to the potential to test for specific breakdown products in biological or soil samples. The authors chose to focus on sulfur mustard-related attacks in their report to the Department of Homeland Security partly because of the technical prowess its production suggests.
[e] Figures on deaths and casualties are incomplete and often inconsistent, particularly where chlorine or commercial toxic chemicals were employed. The following casualty figures for mustard agent are, however, reasonably well supported: one minor was killed following mustard agent exposure at Marea, Syria, in August 2015. See “S/2016/738: Third report of the Organization for the Prohibition of Chemical Weapons-United Nations Joint Investigative Mechanism,” United Nations Security Council, August 24, 2016. Thirty-five injuries were reported after a mustard attack on a Kurdish Peshmerga position near Makhmour, Iraq, in August 2015. See “Blood tests reveal traces of mustard gas used by IS in attacks on Peshmerga forces,” ARA News, October 9, 2015, and Barbara Starr, Jim Sciutto, and Elise Labott, “U.S. investigating ‘credible’ reports that IS used chemical weapons,” CNN, August 14, 2015. At least three Peshmerga soldiers were injured in a second Makhmour attack in February 2016. See “Peshmerga endure fresh ISIS chemical attack,” Rudaw, February 17, 2016, and Matthew Vickery, “Eyewitness account: ISIL steps up chemical weapons attacks on Kurds in Iraq,” USA Today, March 10, 2016. A Peshmerga officer was seriously wounded in early March 2016. See Peshmerga News, “Major Jamal, brave #Peshmerga who defused many ISIS IEDs, is hospitalized after ISIS used Mustard agent near Zummar,” Twitter, March 4, 2016. This comprises a total of one confirmed death and 39 probable injuries. Other reports were not evaluated for their credibility due to imprecise or inconsistent numbers.
[f] This figure is based on open source research by the authors and is included in the report referred in footnote a.
[g] Also identified as trichlorovinylsilane. See “Trichlorovinylsilane,” National Center for Biotechnology Information, PubChem Compound Database.
[h] Testing of samples from a suspected mustard attack against U.S. forces in September 2016 initially suggested mustard agent was used, but subsequent testing produced inconclusive results. Ryan Browne, “US: ISIS did not use mustard agent in base attack,” CNN, September 27, 2016.
[i] The other example is Aum Shinrikyo, which mastered the production of sarin and VX nerve agents.
[j] As to why this campaign ended, plausible explanations include the possibility that AQI had been starved of chlorine supplies. The Iraqi government appears to have suspended chlorine shipments, which may partly be substantiated by high incidences of cholera due to a lack of chlorine for civilian water treatment. See James Glanz and Denise Grady, “Cholera Epidemic Infects 7,000 People in Iraq,” New York Times, September 12, 2007. Otherwise, AQI’s operational latitude may have changed considerably due to the Anbar “Awakening” and the U.S. troop surge.
[k] This is to exclude the plans for a chemical dispersal device as developed by the Sydney plotters and their handler. Otherwise, UWT researchers surveyed 77 international terrorism incidents associated with the Islamic State, all of which occurred between May 2014 and January 2017. The primary purpose of the survey was to derive Islamic State TTPs in sophisticated, high-casualty, and other types of attacks. Another incident that could turn out to have links to Islamic State CW is a chlorine charged IED discovered by Indonesia authorities in a Jakarta mall in February 2015. While the chlorine itself did not disperse and was “crafted inside a cardboard box,” Indonesian police claimed that the culprits were Islamic State foreign fighter returnees. No additional information was supplied by which to analyze this claim. As compared to the Sydney case, as described below, this incident is far more difficult to square as an organizationally driven plot. Kate Lamb, “Indonesian police blame jihadis returning from Syria for chlorine bomb,” Guardian, March 25, 2015.
[l] Researchers reviewed issues #5 through #77 of al-Naba, corresponding to the time period November 15, 2015, through April 20, 2017. This time period covers 14 of the 37 Islamic State-related chemical weapons events considered for the UWT report (eight sulfur mustard related events and six events related to other weaponized chemicals.) Researchers also reviewed all available time-period relevant English issues of Dabiq and Rumiyah, especially in order to account for CW incidents occurring prior to November 2015. Though al-Naba is more exhaustive in its coverage than Dabiq and Rumiyah, it is, in fact, more interesting, in the context of this argument, that these magazines do not mention chemical weapons or chemical releases. After all, the latter two titles were Islamic State’s flagship efforts for Western audiences.
[m] Certainly a more exhaustive search could yield different results. However, in order to keep within the time allotted for the research mentioned, the authors had to restrain their search.
[n] In this case, the target was a Shi`a Turkmen-majority town significantly to the east and south of what was then considered the Makhmour front, approximately 150 kilometers southeast of Mosul. This area was plausibly within the AOR of the Iraqi Army’s Nineveh Operations command, if not along that command’s supply corridor. (There was no evidence, however, that the units under this command had stationed any of their elements in or near the town of Taza Khurmatu.) BBC News reported that 24 “shells and rockets” fell on Taza Khurmatu on March 8. VICE News claimed “more than 40 rockets,” alleging that all of these carried chemical warheads. A Shi`a Popular Mobilization spokesman told Al-Sumaria news that two more “Katyusha” rockets had struck on the evening of March 11. See Nafiseh Kohnavard, “Iraqi town Taza ‘hit in IS chemical attack’ appeals for help,” BBC News, March 25, 2016, Campbell MacDiarmid, “Inside Taza, the Iraqi Town Gassed by the Islamic State,” VICE News, March 9, 2016, and “Taza Subjected to New Attack by Ordnance Carrying Toxic Gas,” Al-Sumaria, March 11, 2016.
[o] This observation is not intended as an explanation for the 2017 cessation of Islamic State CW use in theater, which was likely driven by other factors, including loss of personnel, infrastructure, and territory.
[p] The exception may be the Sydney hydrogen sulfide plot. Nevertheless, the Sydney suspects did not attempt to produce chemical warfare agents, but to weaponize commercially available toxic chemicals. The distinction is very important in terms of the threat posed and the technical sophistication involved.
[q] Australian Federal Police Deputy Commissioner Michael Phelan announced that the suspects were in conversation with a senior Islamic State figure from April 2017. See “AFP and NSWP discuss the two Sydney men charged over terrorist acts.” The conversations were allegedly facilitated by the suspects’ brother, who had traveled to Syria as a foreign figher more than a year before. Phelan characterized these interactions as the provision of inspiration and instruction on how to plan, resource, and then execute a civilian aviation plot. The Islamic State figure was not identified, but this plot is similar to the “virtual planner” model described by Daveed Gartenstein-Ross and others, possibly suggesting an al-Amn al-Khariji operative like Rashid Qassim or Abdselam Abbaoud. See Rachel Olding, “Lebanese authorities monitored Australian bomb plot suspects: minister,” Sydney Morning Herald, August 22, 2017, and Daveed Gartenstein-Ross and Madeleine Blackman, “ISIL’s Virtual Planners: A Critical Terrorist Innovation,” War on the Rocks, January 4, 2017.
[r] Deputy Commissioner Phelan indicates experimentation was conducted, but says that the device itself was “very far” from completion. See “AFP and NSWP discuss the two Sydney men charged over terrorist acts.” See also Rachel Olding and Ava Benny-Morrison, “‘Catastrophic’: How Australia narrowly escaped two ‘sophisticated bomb plots,’” Sydney Morning Herald, August 4, 2017.
[s] Both of these points are arguable. The Sydney Morning Herald alleges that the chemical device target would have been “crowded spaces or public transport.” Olding and Benny-Morrison. As to the handler’s prerogative, see the following footnote.
[t] According to one understanding of Islamic State foreign terrorism operations planning, al-Amn al-Khariji operatives conduct attack creation and logistics largely according to their own cognizance, provided that they respect Islamic State leaders’ strategic vision and mandates. Like the somewhat similar auftragstaktik, or “mission-based tactics,” model used by the Imperial German Army in the late 19th and early 20th centuries, this operational doctrine emphasizes the innovation and initiative of Islamic State controllers.
[u] Whether the “mission-based tactics” model was or continues to be accurate can be disputed for at least two reasons. First, al-Amn al-Khariji operations may have changed after the group lost its primary coordination and training center in late 2016 (months before the Sydney plot). Second, former al-Amn al-Khariji leader Abu Mohammed al-Adnani is said to have involved himself with most of the group’s ongoing operations and was undoubtedly part of the Islamic State’s highest echelon. His successor may have also been routinely involved in decision making, to include the hydrogen sulfide choice. If so, chemical terrorism may feature in an as yet unclear way in Islamic State strategizing. Future evidence surrounding the Sydney incident may be key to understanding its wider associations.
[v] The first widely documented use of CW agents or weaponized industrial chemicals by the Islamic State dates to July 12, 2014. See Jonathan Spyer, “Did ISIS Use Chemical Weapons Against the Kurds in Kobani?” Middle East Review of International Affairs 18:3 (2014): pp. 90-94.
 See “Statement by Pentagon Press Secretary Peter Cook on strike targeting ISIL military commanders,” U.S. Department of Defense, July 1, 2016. Also Aymenn Jawad al-Tamimi, “The Archivist: Unseen Islamic State Military Commanders Manual: Qualities and Manners of the Mujahid Commander,” Aymenn Jawad al-Tamimi’s blog, April 11, 2016.
 Authors’ interview, Hamish de Bretton-Gordon, subject matter expert, April 18, 2017.
 C.J. Chivers, “ISIS Has Fired Chemical Mortar Shells, Evidence Indicates,” New York Times, July 17, 2015.
 Benjamin Cole, “Islamic State’s Search for an Effective Chemical Weapons Strategy,” Tactical Decision Making Research Group, June 16, 2016.
 “Exclusive: Daesh used corrosive chemicals against Iraqi civilians (VIDEO),” Sputnik News, February 25, 2016; David Trayner, “ISIS Unleashes WW1 chemical weapons after finding Saddam Hussein’s secret WMD stash,” Daily Star, February 27, 2016.
 “S/2016/738/Rev.1: Third report of the Organization for the Prohibition of Chemical Weapons-United Nations Joint Investigative Mechanism,” United Nations Security Council, August 24, 2016.
 “UNMOVIC Working Document – Unresolved Disarmament Issues: Iraq’s Proscribed Weapons Programmes,” March 6, 2003, p. 76.
 Jean Pascal Zanders, “Chlorine: A weapons of last resort for ISIL? (Part 1),” The Trench, October 27, 2014.
 Damien Cave and Ahmad Fadam, “Iraq Insurgents Employ Chlorine in Bomb Attacks,” New York Times, February 22, 2007.
 Kirk Semple, “Suicide Bombers Using Chlorine Gas Kill 2 and Sicken Hundreds in Western Iraq,” New York Times, March 18, 2007; Bill Roggio, “Al Qaeda’s Chlorine Attacks: The Dirty War in Anbar,” FDD’s Long War Journal, March 17, 2007.
 All issues of al-Naba are available thanks to Aaron Zelin’s website “Jihadology.”
 Authors’ interview, Hamish de Bretton-Gordon, subject matter expert, April 2017.
 Aside from the subsequent example, see “Daesh Does Not Possess Mustard Agent,” All Iraq News, March 10, 2016.
 “Al-Zamili: Daesh Does Not Possess Chemical Weapons and American Claims are an Attempt to Spread Fear,” All Iraq News, March 10, 2016.
 Examples are numerous. For one, see Orsolya Raczova, “Forget nuclear: Chemical weapons are the real weapons of mass destruction threat,” Global Risk Insights, March 3, 2017.
 John Cantlie, “The Perfect Storm,” Dabiq Issue 9, Al-Hayat Media Foundation, May 2015, p. 77.
 Cantlie. See also Heather Saul, “ISIS Claims it Could Buy It’s First Nuclear Weapon From Pakistan Within a Year,” Independent, May 22, 2015.
 For some sense of the hazards of hydrogen sulfide, please refer to Arvind K. Chaturvedi, Dudley R. Smith, and Dennis V. Canfield, “A fatality caused by accidental production of hydrogen sulfide,” Forensic Science International 123:2 (2001): pp. 211-214.