One of the most horrific moments of the Syrian conflict came in August 2013 when rockets laden with the nerve agent sarin hit Ghouta, a rebel-held area on the outskirts of Damascus. Hundreds of people died and thousands more were injured. It was the deadliest chemical attack anywhere in the world since the 1980s.

Considering that Ghouta had been under fire from Assad’s forces at the time, that the casualties were on the rebels’ side and that the regime had previously admitted possessing chemical weapons, there was one very obvious suspect but the regime insisted it was not responsible, dismissing the accusations as “illogical and fabricated”.

Russia joined in with support for Syria’s denials, as did an assortment of people in the west: university professors, retired CIA agents, “independent” journalists, “anti-imperialists” and more than a few habitual conspiracy theorists. According to them, the sarin attack on Ghouta was a false flag operation by rebels seeking to falsely incriminate the regime and hoping the horror it caused would trigger a full-scale military intervention by western powers to overthrow Assad.

There was no good reason to believe the “false flag” theory at the time and the evidence compiled since then points overwhelmingly to an attack carried out by the regime. Nevertheless, the regime’s defenders persisted in blaming the rebels — a claim that was only worth considering if it could be shown that rebel fighters had access to large quantities of sarin.

Hersh joins the fray

Three months after the attack, under a headline asking “Whose sarin?”, the London Review of Books published an article which soon became a linchpin for the false flag theorists’ claims. Its author was the famous American journalist Seymour Hersh who specialises in sensational stories based on shadowy intelligence sources.

Although Hersh offered no conclusions as to who carried out the attack his article sought to cast doubt on the regime’s culpability while suggesting that rebels could have been responsible.

In the article, Hersh complained that statements from President Obama blaming Assad’s regime for the Ghouta atrocity had failed to acknowledge “that the Syrian army is not the only party in the country’s civil war with access to sarin”. In the months before the attack, Hersh wrote, US intelligence had found evidence “that al-Nusra Front, a jihadi group affiliated with al-Qaeda, had mastered the mechanics of creating sarin and was capable of manufacturing it in quantity”.

The false flag theorists treated that as vindication of their claims and rejected any suggestion that Hersh was wrong. He had, after all, won numerous journalism prizes during his long career, including a Pulitzer 43 years earlier for exposing the Mai Lai massacre in Vietnam. Some of his other exposés had misfired, though, and it emerged that his “Whose sarin?” article had been rejected by The New Yorker and the Washington Post before being accepted by the London Review of Books.

On the question of sarin in rebel hands, Hersh quoted an unnamed “senior intelligence consultant” who told him of a secret document, prepared for the Defense Intelligence Agency’s deputy director, David Shedd, which confirmed that al-Nusra “had the ability to acquire and use sarin”. Al-Qaeda in Iraq (AQI), which was also active in Syria, “understood the science of producing sarin”, according to the consultant.

Hersh gave more details of the document’s contents in a subsequent article published by the London Review of Books in April 2014, quoting it as saying that al-Nusra was engaged in “the most advanced sarin plot since al-Qaida’s pre-9/11 effort”. He later explained that he had cited only a few lines from the document because “I worried about compromising the source of what obviously was excellent intelligence work”.

Earlier this month, however, Hersh published the entire 10-year-old document online — appended to a Substack article in which he accused to US of suppressing or ignoring “politically inconvenient” intelligence regarding the war in Ukraine.

He then drew a parallel with the sarin attack in 2013 when, according to his account, “crucial intelligence” that sarin “was known to be in the hands of the Islamist opposition” in Syria had not reached the White House because it was politically inconvenient. “My reporting at the time made the point that there were two possible suspects for the sarin attack but only one publicly cited by White House,” he continued.

Hersh seems to have thought his argument would be strengthened by revealing the full contents of Shedd’s intelligence briefing — though it actually did the opposite. It showed that by June 2013 — just a few weeks before the Ghouta attack — Syrian rebels had not succeeded in making sarin, let alone the type and quantity used in the Ghouta attack.

What the document said

The document’s first sentence — that al-Nusra elements were engaged in “the most advanced sarin plot since al-Qaida’s pre 9/11 effort” — sounded alarming but, as the second sentence showed, it hadn’t advanced very far: “Arrests in Iraq and Turkey have disrupted the cell’s operations; however we assess the intent to produce advanced chemical weapons remains.” The document added: “To continue with a sarin effort they will need to recruit scientific expertise.”

Two men linked to al-Qaeda in Iraq (AQI) had been captured in May 2013. One of them, arrested by Iraqi forces, was Kifah Ibrahim, a chemistry graduate who had been recruited by an AQI member in 2007 to make poison, the document said. “According to SIGINT [signals intelligence], he produced incomplete formulas for nerve and blister agents.”

The second man was Adil Mahmud who had graduated from a military college in Iraq during Saddam Hussein’s rule and later before transferred to “military industrialisation” where he claimed to have learned about sulfur mustard and sarin. A search of his home after his arrest by Kurdish forces revealed two sarin precursors and an intermediate compound. “We assess this shows real intent to make sarin,” the document said.

It added that this was “by far the most ambitious effort” either man had undertaken”. They “had not produced sarin yet, but were in the process of discovering a pathway”.

Both Adil and Kifah claimed to have favoured using sarin on targets in Iraq rather than Syria. “This may be true for the smaller amounts they planned to make,” the document said, but “we believe the ultimate targets were Syria-based, likely regime or regime supporters”.

The connection with Syria was via al-Nusra’s “emir for military manufacturing” — a man known as Abd al-Ghani, based in Aleppo. Intercepts showed that in April-May Abd al-Ghani had been “talking with both Adil and Kifah about sarin production, and discussing future plans for large-scale Syria-based production”.

The document said: “We don’t have any indications on whether Ghani was acting on his own initiative or by direction from other ANF [al-Nusra] leaders” but “we assess this is [an] ANF-supervised effort”.

The plan was for Kifah and Adil to “perfect a process for making sarin, then go to Syria to train others to begin large scale production at an unidentified lab in Syria”.

The arrests of Kifah and Adil shortly after those discussions with Ghani appear to have caused a serious setback for the project: Adil had been “of significant importance” and Kifah was important enough for Abd al-Ghani to try to get him exfiltrated from Iraq “along with information related to sarin production”.

Around the same time “several Turkey and Saudi-based chemical facilitators were attempting to obtain sarin precursors in bulk, tens of kilograms, likely for the anticipated large scale production effort in Syria” the document said. That resulted in three individuals being arrested by Turkish authorities.

“Facilitators in Turkey and Saudi had particular difficulty procuring white phosphorus [a sarin precursor] and were attempting to buy one chemical that is not a sarin precursor,” the document added. “We assess this indicates these Turkey-based individuals needed Kifah and Adil to begin the production process in Syria.”

Hazards of do-it-yourself sarin

Maybe Hersh hadn’t bothered to re-read the document before posting it but the effect of making its contents public was to debunk his own claims. While it did show that jihadist elements were trying to make sarin it also showed that at the time of the Ghouta attack — contrary to Hersh’s assertions — they had not “mastered the mechanics” of creating sarin or “manufacturing it in quantity”.

Even if they had succeeded in doing so, however, a lot more work would have been needed if they intended to use sarin on the scale seen in Ghouta. While it would be feasible for a chemist, working in a laboratory and taking suitable precautions, to make a tiny amount of sarin, producing several hundred litres (the quantity believed to have been used in Ghouta) is a very different proposition.

Worldwide, there is only one known example of anyone other than a government manufacturing sarin on a significant scale. This was the Japanese doomsday cult, Aum Shinrikyo, which used sarin to kill 12 people on the Tokyo subway and eight others in a separate attack at Matsumoto in the 1990s.

Despite spending $10 million establishing a secret factory, the cult is said to have produced only about 20 litres over a period of two months before something went wrong and it had to be shut down. Twenty litres is less than half what would have been needed to fill just one of the rockets used in Ghouta. The difficulties faced by Aum Shinrikyo were a clear sign that do-it-yourself sarin wasn’t worth the effort.

Chemical markers

There is more than one way to make sarin and clues to the production process can be found by testing it for impurities. The impurities are residues from chemical reactions that take place during production, and different formulas result in different sets of impurities.

Based on that, international investigators eventually established similarities between the sarin detected at the scene of attacks and that produced by the Syrian government. Furthermore, it was a type that appeared to be unique to the Syrian government: no other country or entity was known to have manufactured sarin in quite the same way.

The first distinctive marker chemical to be identified was hexamine. Mainly for safety reasons the government’s sarin was stored as two separate components — methylphosphonyl difluoride (known as DF) and isopropanol — which were mixed in the presence of hexamine shortly before use. The hexamine was added to make the sarin less corrosive and reduce the risk of damage to munitions, but investigators could find no evidence of anyone other than the Syrian government having used it for that purpose.

Investigators later obtained samples of DF from the government’s stocks, which led to the discovery of three more marker chemicals: phosphorus hexafluoride (PF6), isopropyl phosphates and isopropyl phosphorofluoridates. These were also found in samples from the scene of the 2017 sarin attack on Khan Sheikhoun — which the investigators described as “a strong indicator” that the sarin used in that attack “as well as in previous incidents”, had been produced using DF from the Syrian government’s stockpile.

The upshot was that in order to make sarin containing the relevant chemical markers the rebels would have to have known the government’s secret formula and copied its production process.

However, judging by the list of precursors that they allegedly tried to buy in Turkey, the rebels were attempting to use a different formula. UN/OPCW investigators also pointed out that the government’s the formula included hydrogen fluoride (HF) and rebels were unlikely to have been able to replicate it without a “chemical-plant-type” production method. “HF is a very aggressive and dangerous gas and therefore is difficult to handle,” the investigators noted. “The use of HF indicates a high degree of competence and sophistication.”

In the light of all that, the only credible explanation is that the sarin came from the government’s chemical stockpile and was used by government forces. The possibility that rebels might have seized some of it was emphatically ruled out by Syrian government officials who insisted stockpiles had remained under their control at all times — none of their sarin-related chemicals had been lost or stolen.

That wasn’t the only problem with the “stolen sarin” theory. Since the Syrian government’s sarin was not kept in ready-made form, rebels would have needed to steal its separate components. To make it usable, they would also have needed suitable munitions, specialised equipment for filling them and mixing the components— plus a lot of expertise in working with lethal chemicals.