For the first time since President Barack Obama declared in August 2012 that the use of chemical weapons constituted a “red line,” the United States has responded militarily to the Syrian government’s use of these weapons. On the night of April 6, the U.S. military fired a salvo of 59 cruise missiles at Syria’s Shayrat air base, in response to a deadly chemical attack launched from that base earlier in the week. The chemical attack on the northwestern Syrian town of Khan Sheikhoun, according to first responders on the scene, caused at least 84 deaths and injured more than 500 more.

In announcing the strike, President Donald Trump said, “It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons.”

While the strike on Khan Sheikhoun was the deadliest chemical attack since the Syrian government launched rockets filled with sarin nerve agent into the Damascus suburb of Ghouta in August 2013 — killing more than 1,400 men, women, and children — it is far from the first attack since that massacre. Since 2014, rebel-held sections of Idlib, Hama, Aleppo, and elsewhere have been subjected to at least 120 chemical attacks, mostly by helicopters armed with barrel bombs filled with the toxic chemical chlorine. While these attacks were terrifying for the local populace, they rarely caused mass fatalities.

The attack on Khan Sheikhoun was significant not only for the high number of deaths but also for its use of a far deadlier type of chemical weapon. According to Secretary of State Rex Tillerson, the United States has “very high confidence” that sarin was used in the strike. Although this has not yet been independently confirmed, the victims’ symptoms and autopsies are consistent with poisoning by a nerve agent such as sarin.

If the chemical agent used in this attack was indeed sarin, it would either confirm suspicions that the Syrian regime did not destroy its entire chemical weapons stockpile as promised when it joined the Chemical Weapons Convention (CWC) in 2013 or that it has resumed production of these weapons in violation of the treaty. Either way, this latest attack vividly demonstrates that Syria, despite being a member of the CWC, maintains a well-organized capacity to conduct multiple types of chemical attacks in support of the regime’s tactical and strategic objectives.

While the U.S. cruise missile strike targeted one link in the Syrian chemical weapons kill chain, it did not break the chain. National Security Advisor H.R. McMaster recognized as much when he told reporters in the aftermath of the strike: “Obviously, the regime will retain a certain capacity to commit mass murder with chemical weapons beyond this airfield.”

Syria’s chemical weapons attacks are not the work of a mere handful of people — an entire political, military, and scientific apparatus is responsible for orchestrating them. As Samantha Power, Obama’s ambassador to the United Nations, put it, “While their names may be unfamiliar, their brutality is infamous, so they should be as well.”

Based on information released by the U.N., the Organisation for the Prohibition of Chemical Weapons (OPCW), nongovernmental organizations, and the U.S. and European governments, it is possible to construct a picture of the Syrian government’s entire chain of command involved in the research, production, weaponization, planning, and delivery of chemical weapons. The Syrian chain of command for chemical weapons is composed of four tiers: the senior leadership, which is responsible for authorizing the use of these weapons and providing strategic guidance on their employment; the chemists, who produce, transport, and prepare the chemical weapons for use; the coordinators, who provide intelligence on targets and integrate chemical weapons with conventional military operations; and the triggermen, who deliver the weapons to their targets. Together, these individuals and organizations form a chemical weapons kill chain that has so far claimed roughly 1,500 lives and caused more than 14,000 injuries.

The leadership

Given the sensitive nature of using illegal weapons while under international scrutiny, decisions to use chemical weapons are likely made at the highest levels of the Syrian government. At the apex of Syria’s chemical warfare chain of command is President Bashar al-Assad, who has ruled Syria since the death of his father, Hafez al-Assad, in 2000. The United States describes Assad as the “ultimate decision maker for the chemical weapons program.”

According to French intelligence, only Assad and some of his closest advisors are able to order the use of chemical weapons. Maher al-Assad, Bashar’s younger brother, has likely been granted that authority by dint of his close relationship with the president, his prominent role in leading the crackdown on the uprising, and his position as commander of the powerful 4th Armored Division. There is also circumstantial evidence that Maher was directly involved in the planning of the 2013 chemical attack on Ghouta, as his forces spearheaded an assault on the area shortly after the sarin attack, suggesting these attacks were planned in conjunction. In addition, the 155th Missile Brigade, which was responsible for launching the sarin-filled rockets used in that attack, is subordinate to the 4th Armored Division and reports directly to Maher.

The Joint Investigative Mechanism (JIM) created by the U.N. Security Council to identify the perpetrators of chemical attacks in Syria has reportedly included both Assad brothers on a list of Syrian officials responsible for these attacks. A number of the regime’s most senior officials have also been implicated by the United States and European governments in planning these attacks. Given the insular nature of the Assad regime, it is inconceivable that these officials were not acting with the approval of the president.

Indeed, according to Western intelligence officials, President Assad has delegated day-to-day decision-making on chemical weapons use to his senior commanders. These officials include Maj. Gen. Rafiq Shihadah, the former director of Military Intelligence who still serves as an advisor to the president on strategic affairs; Maj. Gen. Muhammad Mahmud Mahalla, the current director of Military Intelligence; Maj. Gen. Jamil Hassan, the director of Air Force Intelligence; and Maj. Gen. Muhammad Khalid Rahmun, the head of the Political Security Directorate. These officials are likely also members of the “crisis cell” established by Assad at the outset of the uprising to coordinate the regime’s response.

Another notable high-ranking regime official linked to Syria’s use of chemical weapons is Brig. Gen. Bassam al-Hassan, a commander in the Syrian Republican Guard and Assad’s advisor for strategic affairs. In this latter capacity, Hassan acts as the presidential representative to Syria’s Scientific Studies and Research Center (SSRC) — the government agency responsible for producing the country’s chemical weapons and ballistic missiles. Thus, Hassan serves as a vital link to the next tier of Syrian officials in the chemical weapons chain of command.

Workers in protective clothing unload a dummy grenade during a press day at the GEKA facility that assisted with the disposal part of Syria's chemical weapon arsenal on March 5, 2014 in Munster, Germany. (Photo credit: NIGEL TREBLIN/Getty Images)

The chemists

The SSRC is the heart of the Syrian chemical weapons program. The organization has its headquarters in the Barzeh neighborhood of Damascus, another branch in Jamraya, and used to oversee a network of chemical weapons production facilities until they were dismantled under the OPCW’s supervision. The SSRC was responsible for the design and production of the short-range improvised rockets, called Volcanoes, that were used in the sarin attack on Ghouta. As the Syrian government agency responsible for developing and producing nonconventional weapons and the means to deliver them, the organization probably also developed the chlorine-filled barrel bombs in use since 2014.

The director of SSRC is Amr Najib Armanazi, a computer scientist by training. Among his duties was overseeing a facility that produced sarin, the same chemical used in the attack on Ghouta. Brig. Gen. Ghassan Abbas is the head of the SSRC branch near Jamraya responsible for what the U.S. Treasury Department terms “chemical weapon logistics.” This is probably a veiled reference to Unit 450, an all-Alawite unit within the SSRC that is responsible for guarding and transporting Syria’s chemical weapons and preparing them for use by military units.

The commander of Unit 450 receives orders to prepare and deploy chemical weapons directly from the regime’s senior leadership. According to the European Union, Abbas has played a key role in organizing the regime’s chemical attacks, including the one on Ghouta. The United States has sanctioned five more SSRC officials — Brig. Gen. Samir Dabul, Brig. Gen. Ali Wanus, Col. Firas Ahmad, Col. Habib Hawrani, and Col. Zuhayr Haydar — for conducting research or providing logistics in support of the regime’s chemical attacks.

The United States, Britain, and the EU have also sanctioned more than a half-dozen entities that serve as front companies for the SSRC. These front companies play a vital role in helping the center acquire foreign technology for its weapons programs in spite of international sanctions or provide technical expertise to the SSRC. For example, one of those front companies, Business Lab, attempted in 2009 to purchase 500 liters of pinacolyl alcohol, which can be used in the preparation of the nerve agent soman. Although Syria initially denied working on soman, the OPCW found traces of pinacolyl at a SSRC facility.

Civil defense rescue workers try to reduce the effects of chlorine gas as they search for survivors after an attack by government forces in Idlib, Syria, on April 4. (Photo credit: FIRAS FARHAM/Anadolu Agency/Getty Images)

The coordinators

Several of the Syrian government’s key military institutions serve as liaisons between the SSRC, the individual units that conduct the attack, and regime forces operating in areas where chemical attacks are taking place. The Republican Guard, Military Intelligence, and Air Force Intelligence have likely identified promising targets and helped de-conflict the chemical attacks to prevent friendly fire incidents. For example, the Assad regime’s chlorine barrel-bombing campaigns in northwestern Idlib province in the spring and summer of 2014 and the spring of 2015 coincided with heavy fighting in that province between the government and rebel groups.

Maj. Gen. Talal Shafiq Makhluf, the commander of the Republican Guard, was sanctioned by the United States for his role in coordinating military operations with chlorine barrel bomb strikes. The Republican Guard is one of Assad’s elite military units, is manned mostly by Alawite officers and soldiers, and has been deployed to some of the most important battles of the civil war.

Brig. Gen. Yasin Ahmad Dahi from Military Intelligence has also been linked to the Syrian regime’s use of chemical weapons. The primary mission of Military Intelligence is to ensure the loyalty of the military, but it also collects and analyzes intelligence and conducts covert operations.

Two Air Force Intelligence officers have been identified as playing key roles in carrying out the regime’s chemical strikes. Col. Muhammad Nafi Bilal was stationed at SSRC headquarters to serve as a liaison between the center and Air Force Intelligence to ensure proper coordination and was also involved in the transport of chemical munitions. Col. Suhayl Hasan al-Hasan is a pro-regime militia commander who coordinated military operations in Idlib during a period when chlorine attacks were occurring.

It is not surprising that Air Force Intelligence has been deeply implicated in coordinating the regime’s chemical attacks. The organization’s mandate extends far beyond matters related to the Syrian Arab Air Force and has long been used by the Assad family to conduct the regime’s most sensitive and covert operations at home and abroad. The Air Force Intelligence branch in Harasta likely served as the staging area for the Volcano rockets that rained sarin nerve agent on Ghouta in 2013.

A mother and father weep over their child's body who was killed in a chemical weapons attack on the Damascus suburb of Ghouta in Syria on Aug. 21, 2013. (Photo credit: NurPhoto/Corbis via Getty Images)

The triggermen

At the end of the Syrian chemical weapons kill chain are two military organizations in charge of delivering the weapons: the Syrian Artillery and Missile Directorate and the Syrian Arab Air Force.

The Syrian Artillery and Missile Directorate was responsible for conducting the 2013 chemical strike on Ghouta. That attack involved approximately eight to 12 Syrian-made 330 mm Volcano rockets, each carrying approximately 50 liters of sarin nerve agent, and at least two Soviet-era M-14 140 mm artillery rockets filled with sarin. The EU has sanctioned four senior leaders in the Syrian missile force for their role in this attack: Maj. Gen. Tahir Hamid Khalil, the commander of the unit; Brig. Gen. Adnan Aboud Hilweh, a commander in the 155th and 157th Missile Brigades; Maj. Gen. Ghassan Ahmed Ghannan, the commander of the 155th Missile Brigade; and Maj. Gen. Jawdat Salbi Mawas, a senior-ranking officer in the missile force. The 155th Missile Brigade, which is equipped with Scud missiles and is based in the Qutayfa area outside of Damascus, reports to Maher al-Assad through his role as commander of the 4th Armored Division.

Syria is believed to have developed chemical warheads for a range of missiles, including Scuds. The 155th Missile Brigade’s experience operating Syria’s chemical-armed missiles would have been invaluable for deploying and launching the sarin-filled rockets used in the Ghouta attack.

The Syrian Arab Air Force is the other key player in delivering Assad’s chemical weapons. The air force’s primary role has been in using helicopters to conduct more than 100 chlorine barrel-bomb attacks against rebel-held towns in 2014 and 2015, with dozens more attacks occurring in 2016 and 2017. The JIM definitively linked three of these attacks on towns in Idlib to helicopters operating out of the Hama and Humaymim air bases, which are home to the 253rd and 255th squadrons of the 63rd Helicopter Brigade and the 618th naval helicopter squadron. All three of these units are equipped with Mi-8 helicopters or related models, which have played a well-documented role in conducting conventional and chlorine barrel bomb attacks.

The United States has confirmed reports by local activists that the April 4 attack on Khan Sheikhoun was conducted by an Su-22 aircraft based at Shayrat air base. This base is home to the 50th Air Brigade, which contains two squadrons of Su-22s: the 677th and 685th. Shayrat was also one of at least seven Syrian air bases that had the capability to load sarin or its precursors into bombs before these sites were dismantled by the OPCW. According to French intelligence, Syria had a stockpile of aerial bombs designed to deliver 100-300 liters of sarin. These bombs were designed as binary chemical weapons that contain two separate nontoxic precursor chemicals that could be mixed within the bomb shortly before takeoff to produce sarin. Syria may have retained as many as 2,000 of these munitions after joining the CWC. The type of munition used in the attack on Khan Sheikhoun has not yet been determined.

The United States and EU have imposed sanctions on the entire chain of command of the Syrian Arab Air Force for their role in chlorine barrel bomb attacks, including Maj. Gen. Ahmad Ballul, the commander of the air force; Maj. Gen. Saji Jamil Darwish, who oversaw air operations in northern Syria as commander of the 22nd Air Division; Brig. Gen. Badi Mualla, the commander of the 63rd Air Brigade, which was responsible for the helicopters based at Hama air base; and Brig. Gen. Muhammad Ibrahim, the deputy commander of the brigade. Since Shayrat air base is part of the 22nd Air Division, Darwish would also have been involved in planning the attack on Khan Sheikhoun.

U.S. Ambassador to the United Nations Nikki Haley holds up photos of Syrian victims of a chemical weapons attack during an April 5 meeting of the Security Council at U.N. headquarters in New York. (Photo credit: DREW ANGERER/Getty Images)

A path to justice?

This list of Syrian officials and entities that have played a role in chemical attacks during the Syrian civil war is no doubt incomplete. For example, the identities of the commanders of the 50th Air Brigade and subordinate squadrons that were involved in the attack on Khan Sheikhoun are not publicly known. Hopefully, further investigations by the United Nations and nongovernmental groups into war crimes and crimes against humanity committed by the Syrian regime will bring to light a fuller list of those who should be held accountable for using chemical weapons. None of these individuals — from the leader of the country to the pilot who pulled the trigger — should be immune to the consequences of their actions.

Bringing these criminals to justice, however, will be a long, slow, and difficult process. Many individuals who comprise Syria’s chemical weapons kill chain were listed in a U.N. Security Council resolution that was vetoed by Russia and China on Feb. 28. Syria’s lack of membership in the International Criminal Court, and the veto by Russia and China of a Security Council resolution to refer Syria to the court, means that this venue is likely off limits for the foreseeable future.

So far, the only concrete steps to hold these individuals accountable for their actions are financial sanctions and travel bans imposed by the U.S. and European governments. Although the sanctions themselves are largely symbolic, by identifying these individuals and specifying their role in the chemical attacks, the United States and its European allies are laying the groundwork for future prosecutions once Assad is no longer in power. In the case of Iraq, it took almost 20 years for Saddam Hussein and Ali Hassan al-Majid, nicknamed “Chemical Ali,” to stand trial for ordering the use of chemical weapons against the Kurds in 1988.

Nonetheless, “naming names,” even when the ability of the international community to punish these perpetrators in the near-term is limited, has value. Identifying and punishing the perpetrators of these heinous crimes is not only to right past wrongs but to prevent future harms. As Nikki Haley, the U.S. ambassador to the U.N., explained after the Russian veto of the first sanctions resolution, “None of us should hesitate to impose consequences for these attacks. No one else should get the idea that they can use chemical weapons.”

Attribution is the first step to accountability, which forms the basis for deterrence. But attribution without consequences will only embolden the perpetrators, demonstrate to other dictators that the use of chemical weapons is tolerable, and badly damage the global norm against the use of these barbaric weapons. Hopefully, the cruise missile strike on Shayrat air base will deter future Syrian chemical attacks. At the same time, we should not confuse limited military strikes on infrastructure that can be easily repaired as having the same lasting value for deterrence and justice as holding individual government officials and military officers accountable.

In the aftermath of the attack on Ghouta, I co-wrote an article arguing: “[A]n effective effort to reduce the long-term risk of chemical weapons … must also include legal and economic steps to deter further chemical attacks, including by holding individual perpetrators accountable.” In 2017, as in 2013, the use of military force is just one part of a comprehensive strategy to enhance deterrence, bring justice to the victims of chemical attacks, and reinforce the norm against chemical weapons.

Top photo credit: Getty Images/Foreign Policy illustration