Use of chemical weapons in the Syrian civil war

In July 2012, Syrian foreign ministry spokesman Jihad Makdissi stated that the Syrian armed forces would never use chemical weapons against domestic opposition, while remarking that these weapons remained available for use against "external aggression". Syria is thought to have the world's third-largest stockpile of chemical weapons, and opposition forces are concerned that the regime may use them as a last resort to retain power. In August 2012, the United States warned that the use of such weapons was a "red line" for the Ba'athist regime, and would result in "enormous consequences" if crossed. Similarly, France and the United Kingdom have warned of severe consequences for the use of chemical weapons, with France in particular promising a "massive and blistering" response.

In September 2012, the Syrian military began moving its 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, US Defence Secretary Leon Panetta stated that the Syrian regime 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.

Allegations that chemical weapons have been used in Syria first began to emerge on 23 December 2012, when Al Jazeera released unconfirmed reports that a gas attack killed 7 civilians in the rebel-held al-Bayyada neighbourhood of Homs. Less than a month later, a leaked U.S. cable revealed that American officials felt there was a "compelling case" for the use of Agent 15 by regime forces. The White House subsequently rebuked this by stating that "the reporting we have seen from media sources regarding alleged chemical weapons incidents in Syria has not been consistent with what we believe to be true about the Syrian chemical weapons program".

On 19 March 2013, new unconfirmed reports surfaced that SCUD missiles armed with chemical agents may have been fired into the Khan al-Asal district in Aleppo and the Al Atebeh suburbs of Damascus, with both sides accusing each other of carrying out the attack. According to a spokesman for the Free Syrian Army, the attack occurred in rebel territory, though Reuters photographs showed images of Syrian government soldiers injured in the attack. An unnamed Reuters photographer described the gas as having a "chlorine-like smell" and claimed to have witnessed victims suffocating. Officials from within the United States government disputed this claim and stated that there had been no substantive evidence of chemical warfare in Syria, although President Obama reiterated the American stance that such a move coming from either side would be a "game changer" and might prompt international intervention in the war-torn Middle Eastern nation. Meanwhile, the Russian government sided with the Syrian government and blamed the rebels for the attack. Within weeks, the Assad government accused the UN of attempting to extend an investigation in Khan al-Asal to the rest of the country and declared that it would not tolerate such a move.

Zahir al-Sakit, a former Syrian army general from the chemical weapons branch, said he was instructed to use chemical weapons during a battle with the FSA in the southwestern area of Hauran. But instead, Sakit disobeyed the orders and swapped the chemicals with disinfectant water he called "Javel water".

On 13 April, The Times reported that British military scientists have found forensic evidence of chemical weapons being used in the conflict, after examining a soil sample smuggled out of Syria. The perpetrators of the probable gas attacks remain unknown.

An 23 April 2013 the New York Times reported that the British and French governments had sent a confidential letter to the United Nations Secretary General, claiming that there was evidence that the Syrian government had used chemical weapons in Aleppo, Homs, and perhaps Damascus. The United States did not acknowledge this claim at this time, which the New York Times article speculated was because President Obama had promised to intervene militarily if chemical weapon use was proven, and the United States would prefer not to be forced to enter the war right now. Israel also claimed that the Syrian government had used chemical weapons on 19 March near Aleppo and Damascus. By 25 April the U.S intelligence assessment was that the Assad regime had likely used chemical weapons – specifically sarin gas. However, the White House announced that "much more" work had to be done to verify the intelligence assessments. Syria has refused an investigation team from the UN from entering Syria, though Jeffrey Feltman, UN under-secretary for political affairs, said on Wednesday that a refusal would not prevent an inquiry from being carried out.

On 29 April, another chemical attack was reported, this time in Saraqib, in which 2 died and 13 were injured. The injured were taken to Turkey. On 5 May, Turkish doctors confirmed that no traces of sarin had been found in the blood samples of victims. The same day, members of the United Nations independent commission of inquiry on Syria said it had 'gathered testimony – indicating' rebels had used the nerve agent sarin in attacks. Commission member Carla del Ponte said that there were 'strong, concrete suspicions but not yet incontrovertible proof of the use of sarin gas', from the way the victims were treated". Del Ponte gave no details as to when or where sarin may have been used. The Commission later clarified that it had no conclusive findings that any party has used chemical weapons. A senior United States White House official, Jay Carney, cast doubt on the idea that rebels could use chemicals weapons, or even possess them. Carney also noted that Del Ponte does not work on the UN team leading the investigation. Carney went on to say "We find it highly likely that any chemical weapon use that has taken place in Syria was done by the Assad regime. And that remains our position".

It is believed the military research center, which Israel struck on 5 May, held chemical weapons.

After clandestinely spending two months in Jobar, Damascus, several reporters for the French news media Le Monde personally witnessed the Syrian army's use of chemical weapons on civilians.

A U.N. report stated that there are "reasonable grounds" to believe that limited amounts of chemical weapons have been used in at least four attacks in the civil war, but more evidence is needed to determine the exact chemical agents used or who was responsible. Stating that it has not been possible "to determine the precise chemical agents used, their delivery systems or the perpetrator."

In June 2013, British and French authorities claim to have evidence that Sarin nerve gas has been used in Syria, these findings and evidence have been passed on to the US government. The evidence is largely made up of samples of bodily fluids taken from individuals who claim to have been affected. However both countries admitted that they cannot prove with "100% certainty" their claims.