In the early hours of August 21, a series of alleged chemical attacks struck various suburbs of Damascus, the bulk of them in neighborhoods that together make up an area east of the city center known as Eastern Ghouta. Among the neighborhoods targeted  just after 2 AM were Jobar (the site of a previous chemical disbursal), Zermalka, Ayn Tarma, Douma, Arbeen, Saqba and Harasta. Yet another hit, this one in the southwestern district of Moadamiya, which is close to the elite Fourth Division’s airbase in Mezze, was also reported.

The death toll varies from the high hundreds to over 1,500. But the scores of videos of civilian and rebel victims uploaded to the Internet give a gruesome indicator that the carnage may only increase as more and more sufferers languish without adequate medical care. Some of these videos show young children in a state of total shock, responding listlessly to treatment or marveling at the fact that they are still alive. Others videos show adults foaming at the mouth and convulsing, or corpses lying in neat rows on the ground, wrapped in shrouds.

By early Wednesday evening, a senior Obama administration official told the Wall Street Journal that Washington has “strong indications” that the Assad regime was behind these latest atrocities. Israeli Defense Minister Moshe Ya’alon was the first U.S. ally to state unequivocally that Damascus was indeed the culprit. (Israel’s intelligence on Syria is considered the best in the world.)

I spoke with two doctors from Douma yesterday. The first, Dr. Majed Abu Ali, the communications manager of Douma city medical office, which is part of the medical office of Eastern Ghouta, said that in his district alone, about 630 cases of exposed patients had been observed with symptoms including respiratory failure, muscle spasms, confused mental states, and pinpoint pupils. “Thirty-six of these cases needed ventilation and intubation, and 16 also had to be sent to the ICU.”

Because of how ill-equipped his team was for handling so large a casualty figure all at once, Dr. Abu Ali said that his own personnel did not take the necessary precautions before treating those possibly exposed to a deadly agent. For instance, they failed to remove the tainted clothing of patients and some of the medical staff became exposed secondarily and required their own treatment regimens as a result.

The Douma medical office fielded patients from around eight separate attacks. According to Dr. Abu Ali, the attacks were against rebel-held positions in Eastern Ghouta while the last two struck “civilian neighborhoods.” The latter attacks “were ten times more severe in terms of casualties than the previous ones. Injuries from [the rebel-held areas] numbered around 63. From the civilian areas, around 600,” Dr. Abu Ali reported.

More than 50 percent of those affected were women and children. Not all patients responded to atropine, a drug commonly administered to counteract nerve agent exposure, evidently due to the intense concentration of whatever was used. Thousands of atropine injections were given, and supplies of the medicine were running low.

I also spoke with Dr. Khaled Ad’doumi, director of Douma city medical office, and asked if his staff were able to determine the exact substance used. “We already know from [a] medical study we conducted that the symptoms of exposure to organophosphate compounds are similar to the ones we observed yesterday.” These compounds, alleged to have been used in prior chemical attacks in Syria, including the one in Khan al-Assal which the UN is meant to investigate, are the basis for many industrial pesticides. They are also used to make sarin and VX gas. Dr. Ad’doumi believes adamantly that sarin was used by no one other than the regime.

Gwyn Winfield, the editor of CRBNe, a journal which monitors unconventional weaponry, told Foreign Policy “No doubt it’s a chemical release of some variety — and a military release of some variety.” He thinks, though, that whatever substance was deployed was not in a purified form. In a subsequent appearance on CNN, Winfield said: “It may well be that this was some kind of an Assad homebrew where he has managed to get elements of an organophosphate, mix it with other chemicals, and then delivered it onto these people.” Winfield also noted that the perpetrator can only have come from the military. “This isn’t a small rogue element; this isn’t a small group. This is a concentrated, well-organized attack by a significant player.”

A chemical “cocktail” of varying agents might account for the reported contradictions in symptoms exhibited all over Damascus yesterday.

Dr. Ad’doumi said that most fatalities his office saw were caused by suffocation. “We had to make choices of who is going to die and who will survive because of the shortage of medical supplies and medical personnel.” At the time I spoke to him — around 3 PM EST — he estimated the death toll at 1,600 in Eastern Ghouta alone. (These figures cannot be independently verified.) And exact casualties, he said, could not yet be determined. But of the total number of Syrians affected by the attacks, he claimed that his facility only treated about a quarter.

A major factor Dr. Ad’doumi attributed to the high patient rate is that many Syrians in Damascus kept their windows open all night and were exposed while they slept. My colleague James Miller, who has analyzed much of the evidence emerging from these attacks, told me that a source of his in Damascus believes that so many children were affected because Eastern Ghouta is routinely shelled. He said, “a lot of the kids go to basements when the explosions happen, often to sleep. But the gas was heavy, and stayed low to the ground, traveling right into the basements and trapping them there.”

According to Human Rights Watch (HRW), which reviewed satellite imagery of Eastern Ghouta, “the affected neighborhoods are predominantly residential with some warehouses, markets, and assorted commercial facilities on the periphery, adjacent to the main highways.”

HRW did not have any evidence to suggest that, whatever substance was used, this was the result of a conventional round accidentally striking a chemical or gas facility in the surrounding area. The New York-based NGO also spoke to one doctor working in the medical center at Arbeen who claimed that activists told him 18 missiles were fired “from the direction of the October War Panorama, a military museum in Damascus city, and of Mezzeh military airport, hit Zamalka, Ayn Tarma, Douma, and Moadamiya.”

The Syrian Support Group (SSG), a U.S.-licensed rebel aid provider, cited one very early report that preceded the HRW briefing that was relayed by Mohammed Salaheddine, a journalist with AlanTV and an eyewitness to the early-morning attacks. Salaheddine claimed that four rockets hit Eastern Ghouta, the first striking Zamalka, the second Ayn Tarma, the third Jobar, and the fourth Zamalka again. He said these were all Grad 122-mm rockets and came from the Damascus-Homs highway near the Baghdad Bridge (southern Damascus), and the other two came from Qabun (north of Jobar). (Note that the Baghdad Bridge is near the Nusariyeh chemical research facility, which the regime currently controls.)

These attacks appeared to have preceded a rapid buildup of conventional military forces around Easter Ghouta which, according to Salaheddine, included 30 tanks and “several thousand regime soldiers.” Non-chemical rocket attacks continued from the direction of Mezze Air Base in Moaddamiya, presumably launched by the Fourth Division. “Large explosions could be heard in the background during the call with Mohammad,” the SSG emailed.

Eastern Ghouta is a rebel-held area where the Free Syrian Army-affiliated units, as well as some Salafist-jihadist groups including al-Qaeda, have firmly established themselves to a degree few Syria watchers appreciate. The regime has thrown everything it has against this area, including chemical weapons, because it’s not only a strategic launchpad for further incursions into central Damascus, it is also home to one formidable rebel groups in the south:  Liwa al-Islam.

Last summer, this brigade was responsible for the assassination of several high-ranking members of Assad’s “crisis management cell,” including Bashar’s own brother-in-law and longtime Syrian security chief Assaf Shawkat. Any gains the regime may have made to flush out the rebels from Eastern Ghouta have been swiftly reversed. (One source told me a possible motive the regime may have had to strike so furiously today was that Saudi Arabian-purchased weapons, mainly anti-tank munitions, may have been recently delivered to FSA affiliates in this area. Rebels here have also raided regime stockpiles in recent days.)

Still, many will speculate as to why the regime would launch such a catastrophic chemical attack days after the arrival of a 13-man UN inspection team in Damascus tasked with investigating claims of prior chemical weapons uses. That team had to strenuously negotiate the remit of its mission and agree to only inspect three sites where the alleged attacks took places many months ago and where any soil or blood samples will have long since been degraded. It also agreed not to enter any area in Syria where regime military operations were underway. This of course would include Eastern Ghouta, and that inked stipulation may have been part of the regime’s logic in brazenly gassing so many within a few minutes drive from where the UN inspectors were being hosted. It appears unlikely in the extreme that they will gain access to any of Wednesday’s target sites.

The regime and its main European ally, Russia, also have not coordinated their responses to the latest accusation of war crimes. Damascus denies that any chemical agent was used. “These are lies that serve the propaganda of the terrorists,” one official said. “We would not use such weapons.” The Russian Foreign Ministry, meanwhile, first began by calling for a “professional” forensic investigation, then concluded that the rebels were responsible for a “premeditated provocation”. This made any UN Security Council consensus on reaching a resolution obviously impossible.

If these reports are confirmed, they will amount to the single deadliest deployment of chemical weapons since Saddam Hussein gassed Iraqi Kurds at Halabja in 1988. They will also undoubtedly embarrass whatever remains of the Obama administration’s policy on Syria. A year ago to the day, the president established his so-called “red line” against the Assad regime’s use or mass mobilization of chemical weapons. But since then, and as more evidence of such use (and such mobilization) has accrued and been corroborated by a host of Western and regional intelligence agencies, Washington’s position has been quietly “revised.” One unnamed U.S. intelligence official put it like this to Foreign Policy earlier in the week: “As long as they keep the body count at a certain level, we won’t do anything.”

Leaving aside what an official in even this White House might imaginatively characterize as the appropriate number of asphyxiated per day, it seems clear that a new benchmark has indeed been reached. The deaths of so many in so little time, whatever caused them, cannot have been faked.

“The White House is going to be hard pressed to construct an answer to this one,” Charles Duelfer, a former U.S. weapons inspector, told the Guardian. “It was easy to waffle a bit so long as alleged use was minor and didn’t happen again, but this is really putting the administration in a corner.”

I wish I shared Duelfer’s expectation of what it now takes to shame the United States into action in the Middle East. But perhaps the least that can be said of this latest dispatch from hell is that yesterday was not the best of all days for Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, to write to Congress yet again reaffirming his boss’s opposition to military intervention in Syria.

source