[11][12][13] Human Rights Watch has documented 85 chemical weapons attacks in Syria since 2013, and its sources indicate the Syrian government is responsible for the majority.

[14] People reported incidents of chemical weapons use specifically in Douma in January 2018; Russia vetoed a potential United Nations mission to investigate.

[26][27][28] On 31 March, the last of the evacuations was conducted and the Syrian army declared victory in Eastern Ghouta, while the rebels that were still holding out in Douma were given an ultimatum to surrender by the end of the day.

"[32] SAMS also said a chlorine bomb struck a Douma hospital, killing six people, and that another attack with "mixed agents" affected a building nearby.

[33] According to the Syrian opposition groups, witnesses also reported a strong smell of chlorine and said effects appeared stronger than in previous similar attacks.

[34] Several medical,[35] monitoring, and activist groups[36]—including the White Helmets—reported that two Syrian Air Force Mi-8 helicopters dropped barrel bombs on the city of Douma.

In September 2018 the United Nations Commission of Enquiry on Syria reported: "Throughout 7 April, numerous aerial attacks were carried out in Douma, striking various residential areas.

"[1]: 9.12  The OPCW said it found no evidence to support the Assad government's claim that a local facility was being used by rebel fighters to produce chemical weapons.

[51] CBS journalist Seth Doane also traveled to Douma on 16 April, finding the site of the alleged attack where a neighbor reported a choking gas that smelled like chlorine.

[52] Eliot Higgins, a citizen journalist, founder of Bellingcat, and blogger investigating the Syrian civil war,[53][54] concluded based on geographical, video, and open source evidence that the chlorine gas was dropped by one of two Mi-8 helicopters taking off from Dumayr Airbase 30 minutes earlier.

[57] The Guardian reported testimony from witnesses that medical personnel in Douma faced "extreme intimidation" from Syrian officials for them to remain silent about their patients' treatment.

"[59] In June 2018, a New York Times investigation found that Syrian military helicopters dropped a chlorine bomb on the rooftop balcony of an apartment building in Douma.

[60] The investigations published soon after the fact by Bellingcat, the New York Times, and Forensic Architecture were later confirmed by an in-depth report by James Harkin and Lauren Feeney in The Intercept.

[63] After six months of examining the evidence, interviewing witnesses, and consulting with experts such as Higgins and Theodore Postol of the Massachusetts Institute of Technology, Harkin and Feeney concluded that Syrian Air Force helicopters dropped two chlorine canister bombs on Douma on 7 April 2018.

According to Harkin, the frightened residents seen flocking to a nearby hospital and being doused with water in viral footage were not survivors of the chemical attack, but victims of conventional weapons and smoke inhalation.

[69] In December 2024, as the Assad government fell, journalists from the BBC and The Guardian were able to interview witnesses and survivors in Douma, who described how they'd been prevented from speaking in the years since the incident.

According to a US State Department spokeswoman, there was "credible information" that "Russian officials are working with the Syrian regime to deny and to delay these inspectors from gaining access to Douma," and "to sanitize the locations of the suspected attacks and remove incriminating evidence of chemical weapons use.

During the visit to Location 2 (cylinder on the roof), Syrian Arab Republic representatives did not provide the access requested by the OPCW Fact-Finding Mission (FFM) team to some apartments within the building, which were closed at the time.

[86]In March 2019, the OPCW FFM final report concluded: Regarding the alleged use of toxic chemicals as a weapon on 7 April 2018 in Douma, the Syrian Arab Republic, the evaluation and analysis of all the information gathered by the FFM—witnesses' testimonies, environmental and biomedical samples analysis results, toxicological and ballistic analyses from experts, additional digital information from witnesses—provide reasonable grounds that the use of a toxic chemical as a weapon took place.

"[89] Russia threatened to block the budget for the OPCW at the annual meeting in The Hague in 2019 if it included funding for a new team which would give the organisation powers to pin blame on culprits for the use of toxic arms.

"[90] On 28 November 2019 the bid by Russia to block funding for a new team that will identify culprits behind toxic attacks in Syria failed with member states at the global chemical watchdog overwhelmingly approving a new budget.

[93] The third report published in 27 January 2023 by the OPCW Investigation and Identification Team (IIT) concluded that the Syrian Armed Forces were responsible for the chemical attack.

"[94][95] In a joint press release published by the US Department of State on the same day, the Foreign Ministers of United States, UK, France and Germany thanked the OPCW for its "independent, unbiased, and expert" research and denounced the Syrian government for its continuing violations of Chemical Weapons Conventions, stating: "Our governments condemn in the strongest terms the Syrian regime’s repeated use of these horrific weapons..Syria must fully declare and destroy its chemical weapons program and allow the deployment of OPCW staff to its country to verify it has done so... IIT also obtained information that, at the time of the attack, the airspace over Douma was exclusively controlled by the Syrian Arab Air Force and the Russian Aerospace Defence Forces.

"[96] France – On 12 April, French President Emmanuel Macron said he has proof that the Syrian government attacked the town of Douma with chemical weapons and at least used chlorine.

Such claims and accusations [about chemical weapons use] by the Americans and some Western countries signal a new plot against the government and nation of Syria and is an excuse for military action against them.

[100] Russia – On 13 March 2018 the Chief of the General Staff of the Russian Armed Forces, Valery Gerasimov, said the Russian military had "reliable intelligence" that suggested the rebels holding Eastern Ghouta, along with the White Helmets activists, were preparing to stage and film a chemical weapons attack against civilians, which the U.S. government would blame on the Syrian forces and use as a pretext to bomb the government quarter in Damascus.

[109] On 26 April, Russian officials held a press conference in The Hague where they presented several apparent witnesses from the Douma incident, flown in from Syria, who said that reported victims had not suffered symptoms of a chemical attack.

[114] Saudi Arabia – The Ministry of Foreign Affairs condemned the use of chemical weapons, and stress the need for a peaceful solution based on the principles of the Geneva Declaration and UN Security Council resolutions.

[123] On 10 April, Trump, UK Prime Minister Theresa May, and French President Emmanuel Macron said in a statement following joint telephone calls that they had "agreed that the international community needed to respond to uphold the worldwide prohibition on the use of chemical weapons".

[131][132] World Health Organization – The WHO released a statement, with a reference to outside medical sources,[133] that 43 people died while suffering "symptoms consistent with exposure to highly toxic chemicals.