Timeline of chemical weapons in Syria
July 23: Syrian Foreign Ministry spokesman Jihad Makdissi confirms that Syria has chemical weapons.
August 20: President Obama warns that chemical weapons are a “red line” and threatens “enormous consequences” if the United States sees “a whole bunch of chemical weapons moving around or being utilised in Syria”.
December 23: First report of chemical weapons use: rebels say seven people were killed in Homs when aircraft dropped “poisonous materials”.
March 19: Alleged chemical attacks in Khan al-Assel (Aleppo) and al-Atebeh (Damascus), reportedly killing some 25 people. Regime blames rebel fighters and calls on UN to investigate.
March 26: UN secretary-general appoints Swedish professor Åke Sellström as head of mission to investigate alleged use of chemical weapons in Syria.
August 18: UN investigative mission arrives in Syria.
August 21: Alleged chemical attack in Ghouta area of Damascus.
August 29: British parliament votes against military action in Syria over Ghouta attack – a defeat for the government.
August 29: BBC report shows horrific hospital scenes after a school was hit by an incendiary weapon in northern Syria.
August 29: Mint Press News claims deaths in Ghouta were result of rebels mis-handling chemical weapons supplied by Saudi Arabia.
August 30: President Obama talks of “limited” military action to “help make sure that not only Syria, but others around the world, understand that the international community cares about maintaining this chemical weapons ban and norm”.
September 5: Two US senators propose holding off military action for 45 days to give Syria an opportunity to sign the Chemical Weapons Convention.
September 9: US Secretary of State John Kerry suggests Assad could avert a military strike by handing over Syria’s chemical weapons to the international community.
September 13: Åke Sellström, head of UN mission, submits report on Ghouta investigation; finds “clear and convincing evidence that surface-to-surface rockets containing the nerve sarin were used”.
September 14: Syria informs UN it is joining the Chemical Weapons Convention.
September 17: Assad tells Fox News “anyone can make sarin in his house”.
October 23: Syria submits its chemical weapons declaration listing items to be destroyed under the terms of the Convention.
December 8: London Review of Books publishes article by Seymour Hersh suggesting rebels were responsible for the Ghouta attack.
April 12, 18, 30 and May 22 and 25: Five alleged chlorine attacks on al-Tamanah (Idlib province). More than 150 casualties reported, including eight deaths. FFM later confirms chlorine use “with a high degree of confidence”.
April 16, 2014 – February 15: Series of alleged chemical attacks reportedly affecting Syrian military personnel. Subsequent FFM investigation at request of Syrian government proves inconclusive.
April 21 and 24: Chlorine allegedly dropped from helicopters on Talmenes (Idlib province). Almost 200 casualties reported, including three deaths. Subsequent FFM investigation confirms chlorine use “with a high degree of confidence”.
April 29: OPCW Director-General announces creation of a Fact-Finding Mission (FFM) “to establish the facts surrounding allegations of the use of toxic chemicals” for hostile purposes in Syria.
June 23: Joint UN/OPCW mission reports that all chemical weapons materials declared by Syria have been removed from the country.
August 29: Series of chemical attacks with “dozens” of casualties reported in Kafr Zita (near Hama), beginning in April and ending on August 30. FFM later confirms chlorine use “with a high degree of confidence”.
September 10: FFM report says chemical weapons have been used “systematically and repeatedly” in northern Syria.
March 16 – May 20: Series of alleged chemical attacks in Idlib province (Qmenas, Sarmin, Binnish, Idlib city, al-Nerab, Saraqib, and Kurin). FFM finds “likely” use of a toxic chemical, “probably” containing chlorine.
July 2015: President Assad seeks Russian military assistance to combat “terrorism”.
August 7: UN Security Council unanimously adopts Resolution 2235 establishing for a period of one year a Joint Investigative Mechanism (JIM) to identify perpetrators of chemical attacks in Syria.
August 21: Alleged chemical attack in Marea (Aleppo province). Islamic State fighters suspected. FFM confirms with “utmost confidence” the use of sulfur mustard.
August/September 2015: Russian military build-up in Syria.
July 2016: Blogger Vanessa Beeley visits Syria for first time as a member of US Peace Council delegation. Visit culminates in a two-hour meeting with President Assad.
August 1: Alleged chemical attack in Saraqib (Idlib province), reportedly affecting 26 people. FFM investigation proves inconclusive.
August 2: Alleged chemical attack in al-Awamid district of Aleppo, reportedly killing six people and injuring 20 (military and emergency services personnel). FFM investigation at request of Syrian government unable to “confidently determine” whether or not a specific chemical was used as a weapon and says none of the chemicals identified are likely to have been the cause of death.
August 24: JIM report attributes two chlorine attacks (Talmenes, 21 April 2014 and Sarmin, 16 March 2015) to Syrian government forces and a third one involving sulfur mustard (Marea, 21 August 2015) to Islamic State fighters.
September 16: Two women in Um Hawsh (Aleppo province) injured by alleged chemical attack using mortars. Preliminary investigation by Syrian government with assistance from Russia. FFM later confirms the women were exposed to sulfur mustard.
October 1: Alleged chemical attack in Kafr Zeita (Hama province). FFM finds "reasonable grounds" to believe that a chlorine cylinder was used as a weapon.
October 21: JIM report attributes chlorine attack in Qmenas (16 March 2015) to Syrian government forces.
October 30: Alleged chemical attack in al-Hamadaniyah district of Aleppo. FFM investigation at request of Syrian government unable to “confidently determine” whether or not a specific chemical was used as a weapon.
November 7: UN Security Council renews mandate of JIM for a further year.
November 13: Alleged chemical attack Karm al-Tarrab (outskirts of Aleppo) affecting Syrian military personnel. FFM investigation at request of Syrian government unable to “confidently determine” whether or not a specific chemical was used as a weapon.
November 2016: Vanessa Beleey invited to Moscow, together with Mother Agnes, “to report on the illegal Nato state intervention and dirty war on Syria”. Meets deputy foreign minister and foreign ministry spokeswoman.
March 24: Alleged chemical attack in Ltamenah (Hama province). FFM concludes that sarin was “very likely” to have been used.
March 25: Alleged chemical attack in Ltamenah (Hama province), resulting in death of a doctor at a hospital which was reportedly hit by a gas cylinder. FFM concludes that chlorine was “very likely” to have been used.
March 30: Alleged chemical attack in Ltamenah (Hama province). FFM concludes that sarin was “more than likely” to have been used.
April 4: Alleged chemical attack in Khan Sheikhoun (Idlib province), reportedly causing about 100 deaths. FFM concludes that a large number of people were exposed to sarin.
April 7: US fires 59 cruise missiles at Shayrat Air Base which was allegedly used to launch sarin attack on Khan Sheikhoun.
June 25: German news website Welt publishes article by Seymour Hersh claiming deaths in Khan Sheikhoun were not caused by sarin but by conventional weapons hitting stocks of fertiliser.
June 29: FFM report concludes that “a large number of people, some of whom died, were exposed to sarin or a sarin-like substance” in Khan Sheikhoun on April 7.
September 1: Journalist Seymour Hersh named as winner of the annual Sam Adams Award for Integrity in Intelligence.
October 24: In UN Security Council, Russia vetoes further extension of JIM’s mandate.
October 26: JIM report attributes sarin attack in Khan Sheikhoun (4 April 2017) to Syrian government forces and a sulfur mustard attack in Umm Hawsh (15 and 16 September 2016) to Islamic State fighters.
January 25: Working Group on Syria, Propaganda and Media registers its website.
February 4: Alleged chemical attack in Saraqib (Idlib province). FFM concludes that chlorine was “likely” to have been used.
March 4: Sergei and Yulia Skripal poisoned with nerve agent in Salisbury, UK.
April 7: Alleged chemical attack in Douma on outskirts of Damascus.
April 13: Four Russian agents discovered in car park adjacent to OPCW headquarters, attempting to hack into its wifi system.
April 14: Russian foreign minister Sergei Lavrov mistakenly claims Skripals were poisoned with BZ rather than Novichok nerve agent.
April 14: US, Britain and France launch airstrikes reportedly targeting Syrian government facilities connected with chemical weapons.
April 14: FFM arrives in Syria for deployment to Douma.
May 2: FFM leaves Syria after deployment to Douma.
May 24: UN Secretary-General António Guterres accuses Security Council of failing to meet its responsibility regarding chemical weapons and calls for the creation of “a new and impartial mechanism” to identify those who use them.
May 29: Britain, the US and nine other countries call for a special session of the OPCW’s governing body, the Conference of the States Parties.
June 6: Four OPCW staff, including Brendan Whelan, seek advice from toxicologists on possible exhumation of bodies from Douma and discuss possible cause of death of the alleged victims.
June 26-27: Special session of the Conference of the States Parties approves resolution instructing OPCW to “put in place arrangements to identify the perpetrators of the use of chemical weapons” in Syria. Opposed by Russia, China, Syria and 21 other countries.
July 6: FFM issues interim report on Douma saying it has found no evidence of sarin but is continuing work to establish the significance of “various chlorinated organic chemicals” that were detected.
August 20: Whelan circulates draft minutes of the June toxicology meeting.
August 2018: Henderson engages university professors to assist with his assessment of the Douma cylinders.
August (end of): Whelan leaves OPCW.
November 20-23: At a regular meeting of the Conference of the States Parties, Russia and China call for the formation of “an open-ended group of experts” to consider whether giving the OPCW power to identify perpetrators is in line with the Chemical Weapons Convention. Their proposal is rejected. Meeting also approves budget for the group who will identify perpetrators – now officially known as the Investigation and Identification Team (IIT).
November 24: Alleged chemical attack in Aleppo. FFM unable to establish whether or not chemicals were used as a weapon.
February 28: Struggling to find someone to accept his analysis of the Douma cylinders, Henderson informs OPCW Chief of Cabinet that he has “dropped it off” at the Documents Registration and Archiving department (contrary to regulations).
March 1: FFM issues final report on Douma; finds “reasonable grounds” that a toxic chemical was used as a weapon; adds that the toxic chemical contained reactive chlorine and was “likely” to have been molecular chlorine.
March 11: Syria sends letter to OPCW complaining about the Douma report.
April 11: Working Group on Syria, Propaganda and Media issues 7,000-word critique of the FFM’s report on Douma and says OPCW is not fit to be entrusted with identifying the users of chemical weapons in Syria.
April 26: Russia sends letter to OPCW complaining about the Douma report; asks for it to be made public.
May 13: Working Group on Syria, Propaganda and Media publishes a leaked copy of Henderson’s document.
May 15: Henderson is suspended by OPCW a few days before end of his employment contract.
May 21: OPCW responds to Syrian and Russian complaints about the Douma report.
May 2019: Syria refuses visa for head of IIT; says it does not recognise the IIT and will not cooperate with it.
October 15: “Whistleblower Alex” gives presentation to Courage Foundation panel in Brussels. Claims to have emails, text messages and “suppressed draft reports” showing irregularities in the conduct of the FFM’s Douma investigation.
November 18: Courage Foundation circulates open letter addressed to representatives at the Conference of the States Parties. It calls for all inspectors who took part in the Douma investigation to be allowed to “come forward and report their differing observations in an appropriate forum”. Signatories include film director Oliver Stone and Professor Noam Chomsky.
November 23: WikiLeaks publishes the first “Alex” document – an email from Whelan complaining about changes to the draft report on Douma.
November 25-29: At the Conference of the States Parties a Syrian proposal echoing the Courage Foundation’s call for open debate about Douma fails after gaining support from only six other countries.
December 14: WikiLeaks publishes five leaked documents relating to claims made by “Alex”.
December 27: WikiLeaks publishes four leaked documents relating to claims made by “Alex”.
January 20: Russia hosts Arria formula meeting at UN. Henderson addresses the meeting via video link.
January 22: At a meeting on parliamentary premises in London, Professor Paul McKeigue of the Working Group on Syria, Propaganda and Media claims that the alleged victims of the Douma attack were civilian captives murdered by rebels in a gas chamber.
February 6: OPCW report says Henderson and Whelan committed deliberate, premeditated and serious breaches of confidentiality rules.
April 8: IIT issues its first report, attributing three chemical attacks in Ltamenah to Syrian government forces.
July 9: Conference of the States Parties sets 90-day deadline for Syria to declare the facilities where the weapons used in the Ltamenah attacks had been “developed, produced, stockpiled, and operationally stored for delivery”. Also calls on Syria to declare all chemical weapons currently in its possession and to resolve all outstanding issues regarding its initial declaration.
September 28: Russia and China jointly host Arria formula meeting at UN. Participants by video link include Henderson, Aaron Maté from The Grayzone website and Theodore Postol, an emeritus professor at Massachusetts Institute of Technology.
December 2020: Professor Paul McKeigue of the Working Group on Syria, Propaganda and Media begins three-month email correspondence with “Ivan”, whom he mistakenly believes to be working for Russian intelligence.
March 15: Berlin Group 21 issues “Statement of Concern”.
April 12: IIT issues its second report, attributing a chlorine attack in Saraqeb to Syrian government forces.
April 21: Following Syria’s failure to comply within the 90-day deadline, Conference of the States Parties decides to suspend its OPCW voting rights and bans it from holding any office within the organisation. It says these restrictions will remain in place until Syria complies fully.
May 6: UN High Representative for Disarmament Affairs says OPCW inspections in Syria have detected “a neat [unadulterated] chemical warfare agent, the production of which has not been declared”. The chemical was found “inside storage containers of large volume” – suggesting industrial-scale production.
July 9: Syria informs OPCW that the Douma cylinders have been destroyed by an Israeli airstrike hitting a previously-declared chemical weapons production facility. If true, this means Syria had moved the cylinders – contrary to OPCW instructions – from the location where they were supposed to be safely stored.
Note: This timeline does not include all reported chemical attacks in Syria. It lists those that acquired significance in the political discourse.