Syria's chemical weapons program began in the 1970s with weapons and training from Egypt and the Soviet Union, with production of chemical weapons in Syria beginning in the mid-1980s. Syria's chemical weapons program was one of the largest in the Middle East. For some time, Syria was believed to have the world's third-largest stockpile of chemical weapons, after the United States and Russia. Prior to September 2013 Syria had not publicly admitted to possessing chemical weapons, although Western intelligence services believed it to hold one of the world's largest stockpiles. In September 2013, French intelligence put the Syrian stockpile at 1,000 tonnes, including Yperite, VX and "several hundred tonnes of sarin". At the time, Syria was one of a handful of states which had not ratified the Chemical Weapons Convention. In September 2013, Syria joined the CWC (formally acceding on 14 October), and agreed to the destruction of its weapons, to be supervised by the Organisation for the Prohibition of Chemical Weapons (OPCW), as required by the convention. A joint OPCW-United Nations mission was established to oversee the destruction process. Syria joined OPCW after international condemnation of the August 2013 Ghouta chemical attack, for which Western states held the Syrian government responsible (whilst Syria and Russia held the Syrian rebels of the Syrian civil war responsible) and agreed to the prompt destruction of its chemical weapons.
The destruction of Syria's chemical weapons that the Assad government had declared was completed by August 2014, yet further disclosures, incomplete documentation, and allegations of withholding part of Syria's chemical weapons stockpile since mean that serious concerns regarding chemical weapons and related sites in Syria remain. On 5 April 2017, the government of Syria allegedly unleashed a chemical attack that killed 70 civilians. A suspected chemical attack on Douma on 9 April 2018 that killed at least 49 civilians has been blamed on the Syrian Government.
As of the fall of the Assad regime in December 2024, Syria retained at least some chemical weapons, whose status was thrown into flux with the sudden shift in the Syrian tactical situation. The new government renew full cooperation with OPCW, which re-established its presence in Syria in November 2025. As of May 2026 an OPCW team found more than 70 previously undeclared chemical munitions (rockets and aerial bombs), as well as raw ingredients for the production of sarin. Rockets of the same type as those used in the Ghouta chemical attack were also found.
Prior to entry into force on 14 October 2013 of Syria's instrument accession, Syria was one of five states that had not signed and seven that had not ratified the Chemical Weapons Convention, which prohibits the development, production, stockpiling, transfer, and use of chemical weapons. However, in 1968, Syria acceded to the 1925 Geneva Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases. Syria had repeatedly pledged to ratify the CWC if its neighbouring countries, especially Israel, ratify the convention. In the aftermath of the 2003 invasion of Iraq, Syria stated that it had no chemical weapons, but stated it possessed such weapons in 2012. The Syrian president had earlier alluded to a chemical weapon capability in public statements, in 1990 and 1997.
Western non-governmental organisations stated they believed Syria had an active chemical weapons program.
In September 2013, Syria provided information about its stockpile to the OPCW as part of its disarmament obligations. However, the exact composition of its declared chemical arsenal will not be disclosed to the public, due to OPCW rules.
A number of reasons have been postulated for Syria's adoption of a chemical weapon strategy in the 1980s:
to act as a deterrent to Israeli use of nuclear weapons against Syria
to compensate for the loss of Egypt as a military ally after the signing of the Egypt–Israel peace treaty in 1979
after recognising the limitations of Syrian air power against Israel in the 1982 Lebanon War, Syria adopted an alternative missile strategy, which required a non-high-explosive warhead to compensate for lack of missile accuracy
to act as a deterrent to its powerful neighbour Turkey in any possible dispute.
According to some US analysts, Syria was provided with some chemical weapons and delivery systems prior to the 1973 Yom Kippur War. According to US intelligence reports, Syria began to develop its chemical weapons capabilities in the later 1970s, with supplies and training from the Soviet Union, and likely with equipment and precursor chemicals from private companies in Western Europe. However Syrian production of chemical weapons is not believed to have begun until the mid-1980s. The Director of the US Defense Intelligence Agency said in 2013 that the Syrian program had never become fully independent, and remained reliant on the importing of precursor chemicals.
In 1988, a U.S. analyst described Syria's chemical weapon capability as more advanced than the Iraqi chemical weapons program; however, Israel stated in 1989 that Syria had only the "potential for chemical warfare, but not more than that". In the meantime, a Syrian chemical weapons scientist, dubbed as "the chemist" who was recruited by the CIA from 1988 until his execution in 2001, reported that there was a lab known as "Institute 3,000" near Damascus to manufacture chemical weapons, as later revealed in Joby Warrick's Red Line book.
In July 2007, a Syrian arms depot exploded, killing at least 15 Syrians, as well as 10 Iranians. Jane's Defence Weekly, a U.S. magazine reporting on military and corporate affairs, believed that the explosion happened when Iranian and Syrian military personnel attempted to fit a Scud missile with a mustard gas warhead. Syria stated that the blast was accidental and not chemical related.
A 2007 assessment indicated that Syria was capable of producing several hundred tons of chemical weapon agents per year. Another 2007 report said that Syria was believed to have a stockpile of hundreds of tonnes of chemical weapons agents. Syria was believed to be able to deliver chemical weapons by aerial bombs, surface-to-surface missiles and artillery rockets.
In September 2013, a French intelligence report put the Syrian stockpile at over 1,000 tonnes, including nerve agents and their precursors. This included several hundred tons of Yperite, several hundred tons of sarin, and tens of tons of VX. The report stated that Syria uses a "binary form" technique which demonstrates that Syria has acquired "great knowledge" of chemical weapon technology. As delivery systems the report highlighted as longer-range systems Scud B and Scud C missiles, with a range of 300 and 500 km respectively; and the M-600 (a Syrian version of the Iranian Fateh-110) with a range of 250–300 km. Shorter-range systems include SS21 missiles (70 km); aerial bombs; and artillery rockets and related short-range tactical systems (50 km or less). As of October 2013, some experts believe Syria has around 300 metric tonnes of sulphur mustard and around 700 metric tonnes of nerve agents. By the end of October 2013, the OPCW found a total of 1,300 metric tons of chemical weapons.
According to French intelligence, the Syrian Scientific Studies and Research Centre (SSRC) is responsible for producing toxic agents for use in war. A group named "Branch 450" is allegedly responsible for filling munitions with chemicals and maintaining security of the chemical agent stockpiles.
To provide context for these estimates, 190,000 tons of chemical weapons were manufactured by World War I combatants.