Russia claims that it has definitive evidence linking a chemical-weapons attack in Syria to rebels and not the Syrian army.  In a 100-page report sent in July to the United Nations but announced last night, Russia claims that an inspection conducted by its own team after a March attack in Aleppo shows that composition of the sarin used in the earlier attack was not military-grade, and neither were the delivery systems:

Russia says it has compiled a 100-page report detailing what it says is evidence that Syrian rebels, not forces loyal to President Bashar Assad, were behind a deadly sarin gas attack in an Aleppo suburb earlier this year.

In a statement posted on the Russian Foreign Ministry’s website late Wednesday. Russia said the report had been delivered to the United Nations in July and includes detailed scientific analysis of samples that Russian technicians collected at the site of the alleged attack, Khan al Asal.

Russia said its investigation of the March 19 incident was conducted under strict protocols established by the Organization for the Prohibition of Chemical Weapons, the international agency that governs adherence to treaties prohibiting the use of chemical weapons. It said samples that Russian technicians had collected had been sent to OPCW-certified laboratories in Europe. …

Richard Guthrie, formerly project leader of the Chemical and Biological Warfare Project of the Stockholm International Peace Research Institute, who said he had not seen the original report, said the Russian statement on the makeup of the sarin found outside Aleppo, which the Russians said indicated it was not military grade, might reflect only that “there are a lot of different ways to make sarin.”

He added: “The messy mix described by the Russians might also be the result of an old sarin stock being used. Sarin degrades (the molecules break up) over time and this would explain a dirty mix.”

But he also agreed with the Russian conclusion that the rockets that delivered the sarin in the March 19 incident were not likely to have come from Syrian military stocks because of the use of RDX, an explosive that is also known as hexogen and T4.

This throws a wrench into the works, at least for the moment.  While most assume that the August 21st attack was the first chemical-weapons attack since Barack Obama drew his “red line” a year ago, there have been several such incidents — just on a smaller scale than seen last month.  The reason UN inspectors happened to be on the ground during the August 21st attack was because they were conducting a follow-up investigation of the March incident after receiving the Russian report.

Even if rebels conducted the March attack, it doesn’t mean that Assad’s army is innocent of the August 21st attack.  It does, however, pose two big political problems for Obama internationally and with Congress. Assuming that a UN inspection team uncovers enough evidence about the nature of the chemicals and delivery systems used in August to make it clear that the Assad regime bears the responsibility for the attack, it still leaves the US intervening on behalf of belligerents who may also have used chemical weapons on the battlefield, which undermines the moral argument for military action even further.  And it’s likely that this report will prompt skeptics in Congress to demand a delay until the UN issues reports about both incidents to determine exactly who’s using what in Syria and whether we have any interest in intervening at all.

Of course, the Russian report could just be a big smokescreen of propaganda intended to derail Obama and the US from exerting its influence.  The UN inspection reports should straighten that out, assuming we wait long enough to get them, and that could take quite a while.  But if they can’t give US lawmakers definitive answers on the use of weapons and their sources, will Congress want to open up a new war based on nothing but assumptions?