There have been several instances of chemical weapons attacks during the Syrian civil war, beginning in 2012, which were either reported or corroborated by national governments, the United Nations (UN), the Organisation for the Prohibition of Chemical Weapons (OPCW), Human Rights Watch (HRW), international organizations and media outlets.

Several chemical attacks occurred in different areas of Syria, including Khan al-Assal, Jobar, Saraqib, Ashrafiyat Sahnaya, Kafr Zita, Talmenes, Sarmin and Douma. The deadliest attacks were the August 2013 sarin attack in Ghouta (killing more than 1,729 people and injuring 3,600 patients), the April 2017 sarin attack in Khan Shaykhun (killing at least 89 people) and April 2018 Douma chemical attacks (killing 43 people and injuring 500 civilians), all of which were perpetrated by the military forces of Ba'athist Syria. The most common agent used is chlorine (with one study finding it was used in 91.5% of attacks), with sarin and sulphur mustard also reported. Almost half of the attacks between 2014 and 2018 were delivered via aircraft and less than a quarter were delivered from the ground, with the remaining attacks having an undetermined method of delivery. Since the start of uprisings across Syria in 2011, Syrian Arab Armed Forces and pro-Assad paramilitary forces have been implicated in more than 300 chemical attacks in Syria.

Investigations have found that both the Ba'athist government of Bashar al-Assad and ISIL militants have used chemical weapons, with the vast majority of attacks being carried out by the Assad regime. The OPCW-UN Joint Investigative Mechanism concluded that the Assad regime perpetrated the sarin attack in Khan Shaykhun, as well as three chlorine attacks. They also concluded ISIL militants used sulphur mustard. Investigations launched by the UN's Independent International Commission of Inquiry on the Syrian Arab Republic concluded that the government of Bashar al-Assad carried out 33 chemical attacks between 2013 and September 2018. According to HRW, at least 85 confirmed chemical attacks occurred between 21 August 2013 and 25 February 2018, and concluded that the Ba'athist Syrian military forces were responsible for the majority of the attacks. HRW stated that the actual number of attacks was likely higher than 85. According to a Global Public Policy Institute study, at least 336 chemical attacks occurred between 23 December 2012 and 18 January 2019. The report concluded that 98% of these attacks were carried out by pro-Assad forces and 2% by ISIL.

The Ghouta chemical attack in 2013 prompted the international community to pressure the Syrian Arab Armed Forces to agree to the supervised destruction of their chemical weapons. In April 2018, following at least 18 visits to Syria for inspections, the technical secretariat of the OPCW was unable to "verify that Syria had submitted a declaration that could be considered accurate and complete." The Khan Shaykhun chemical attack on 4 April 2017 drew international condemnation, and resulted in U.S. military action against the Ba'athist Syrian-controlled airbase at Shayrat. The Douma chemical attack on 7 April 2018 also drew a military response from the United States, United Kingdom and France. In April 2021, OPCW suspended Syria from its membership, criticising the Assad regime for not revealing its chemical weapon stockpiles and contravening the Chemical Weapons Convention.

Background

At the outbreak of the Syrian civil war in 2011 concerns were raised about both the security of Syria's chemical weapon sites and about the potential use of chemical weapons. In July 2012, Syrian Foreign Ministry spokesman Jihad Makdissi stated: "No chemical or biological weapons will ever be used... All of these types of weapons are in storage and under security and the direct supervision of the Syrian armed forces and will never be used unless Syria is exposed to external aggression." Bashar Al-Assad himself denied his role ordering chemical attacks and in September 2013, German newspaper Bild claimed to have spoken to a senior intelligence official who claimed Assad did not personally order the chemical attack and that Syrian brigade and division commanders have asked the presidential office for permission to use chemical weapons for more than four months, with permission being denied each time. Journalist Patrick J. McDonnell wrote in the Los Angeles Times in May 2013: "The Syrian government does not publicly acknowledge that it possesses chemical weapons, although international experts say it has a large arsenal, including sarin. Syrian authorities have vowed never to use such weapons against a domestic enemy, even if they were in Syria’s possession. At the same time, however, they have consistently depicted the rebellion against Assad as a foreign-based “conspiracy” hatched by Syria’s enemies abroad, and not as an internal revolt."

A Syrian defector who worked inside the chemical weapons network alleged that in January 2012 two senior Syrian officers moved about 100 kg of chemical weapons materials from a secret military base in Nasiriyah. The Syrian source also described construction of special trucks, which could transport and mix the weapons. These mobile mixers were constructed inside Mercedes or Volvo trucks that were similar to refrigerator trucks. Inside were storage tanks, pipes and a motor to drive the mixing machinery, the defector said. On 23 July 2012, the Syrian government confirmed for the first time that it had chemical weapons, but stated that they would only be used in instances of external aggression.

On 20 August 2012, President Barack Obama used the phrase "red line" in reference to the use of chemical weapons. Specifically, Obama said: "We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized. That would change my calculus. That would change my equation."

In September 2012, the Syrian military began moving chemical weapons from Damascus to the port city of Tartus. That same month, it was reported that the military had restarted testing of chemical weapons at a base on the outskirts of Aleppo. On 28 September 2012, US Defence Secretary Leon Panetta said that the Syrian government had moved its chemical weapons in order to secure them from approaching opposition forces. It emerged that the Russian government had helped set up communications between the United States and Syria regarding the status of Syria's chemical weapons. Russian Foreign Minister Sergei Lavrov stated that Syria had given the United States "explanations" and "assurances" that it was taking care of the weapons. On 8 December, it was reported that members of the jihadist Al-Nusra Front had recently captured a Saudi-owned toxic chemicals plant outside of Aleppo. On 22 December 2012, Russian Foreign Minister Sergei Lavrov stated that Syria had consolidated chemical weapons into one or two places to prevent rebels capturing them, and that recent moves that had alarmed Western governments were part of this consolidation. Brigadier General Mustafa al-Sheikh, a Syrian army defector, confirmed that most of the chemical weapons have been transported to Alawite areas in Latakia and near the coast. Some chemical munitions remain in bases around Damascus. In December 2012 McClatchy reported various chemical weapons experts' skepticism that Syria was preparing to use chemical weapons, noting their "limited utility" in a civil war situation with fluid battlelines, and Syria's comments that such use would be "suicide" in view of US threats of retaliation.mcclatchydc.com, 7 December 2012, Experts skeptical Syria is preparing to use its chemical arsenal

On 6 September 2013 a bill was filed in the US Congress to authorize the use of military force against the Syrian military, mainly in response to the use of sarin in the Ghouta attack on 21 August 2013. On 9 September 2013, the U.S. Secretary of State John Kerry stated that the air strikes could be averted if Syria turned over "every single bit" of its chemical weapons stockpiles. Hours after Kerry's statement, the Russian foreign minister Sergey Lavrov announced that Russia had suggested to Syria that it relinquish its chemical weapons. The Syrian foreign minister Walid al-Moallem immediately welcomed the proposal.

In September 2013 the Syrian government entered into several international agreements for the destruction of its chemical weapons that stipulated an initial destruction deadline of 30 June 2014, a deadline apparently achieved in respect of declared chemical weapons. Prior to September 2013 the Syrian government had not publicly admitted to possessing chemical weapons, although Western intelligence services believed it to hold one of the world's largest stockpiles.

On 17 August 2017, Reuters published a report detailing the extent of Syria's failure to abandon chemical weapons, citing information from investigators, inspectors and diplomatic sources. According to a source cited in the report, "There are certainly some gaps, uncertainties, discrepancies" regarding Syria's chemical weapons arsenal. For example, the Syrian government inaccurately or even falsely declared the types, purposes and quantities of chemicals in its possession, and is suspected of continuing to hold at least 2,000 chemical bomb shells that should have been converted to conventional weapons.

Incidents

Investigation conducted by Dr. Tobias Schneider and Theresa Lutkefend of the GPPi research institute documented 336 confirmed attacks involving chemical weapons in Syria between 23 December 2012 and 18 January 2019. The study concluded that 98% of the total chemical attacks were perpetrated by the Assad regime. Almost 90% of the attacks occurred after Ghouta chemical attack in August 2013.

Reported chemical weapons attacks The table below lists the reported attacks and the main points. See the main articles for details.