Sarin in Syria: what standard of proof?

Mark Fitzpatrick

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Last week, U.S. Defense Secretary Chuck Hagel said it was likely that chemical weapons (CW) had been used on a ‘small scale’ in Syria. President Obama claimed in August that the use of CW in Syria would change his calculus on U.S. intervention, but the intelligence must be examined carefully to assess whether his ‘red line’ on CW has actually been crossed.

The small amount of CW apparently used in Aleppo and Homs raises questions about the third standard: purposefulness. It is still unclear who launched the attack and why.

Mark Fitzpatrick

Last Thursday, the White House said that although it was likely the nerve gas sarin had been used, the evidence was still too thin and that it needed ‘credible and corroborated facts’. President Obama is being pilloried in some quarters for not following through on his earlier red line. But after the misuse of intelligence to justify an invasion of Iraq ten years ago, the bar for concluding that Assad used chemical weapons must naturally be set high. The standard of evidence should meet at least three conditions: clear-cut evidence of use, meaningful quantity, and purposefulness.

As reported in The Times, there seems to be little doubt that chemical weapons were used recently in Syria, probably on at least two occasions. As Jeffrey Lewis argues on ArmsControlWonk.com, the allegation must be specific to time and place. Pictures of victims and media interviews with Syrians who witnessed the attacks are prima facie evidence. The specificity on time of attack is important, to rule out the possibility, for example, that victims came into contact with a punctured or spilt CW canister. The soil samples obtained by British intelligence that show trace elements of a sarin by-product appear to confirm the place where CW were used, although further analysis might be needed to rule out a false positive connected to fertilisers or pesticides.

Even if CW use is confirmed, how much was used is particularly relevant for any retaliatory intervention. When Obama first stated CW use as a red line, he indicated a quantity standard: ‘a red line for us is we start seeing a whole bunch of CW moving around or being utilized.' The low level of by-products found in the soil and the limited number of victims indicates only a small number of CW munitions.

The chain of custody

Obama stopped using a quantity metric after August, but it is still a reasonable criterion. CW are weapons of terror, for use in large numbers to shock and demoralize enemies. The use of only a few CW shells has almost no military or strategic purpose. Assad’s only reason to use CW on a small scale would be to test international reactions before using them on a larger scale to intimidate opponents. When he has other means available for terrorizing them, however, from ballistic missiles to rape, it would seem to make little sense for him to risk using the weapons that are most likely to prompt a Western military intervention. On the other hand, Western analysts have not had a good record at predicting Assad’s risk calculus to date.

The small amount of CW apparently used in Aleppo and Homs raises questions about the third standard: purposefulness. It is still unclear who launched the attack and why. Just as important as establishing the chain of custody of blood samples from alleged victims is clarifying the chain of custody of the armaments. It is not inconceivable that rebel forces overran one of the many CW storage sites in Syria and may have fired a CW shell themselves, perhaps inadvertently.

It would not be the first time that CW injuries were the result of friendly fire. During the Iran-Iraq War, a U.N. investigation confirmed that about 40 Iraqi soldiers had been exposed to a mustard CW agent and a pulmonary irritant near Basra in April 1987. The investigators judged that the cause of this exposure could not be established, however, and they noted that casualties had been close to the front line when they suffered injuries. The likelihood that this was ‘friendly fire’ was reinforced by the fact that Iraq itself was using CW on a massive scale, a situation that obviously does not prevail in the case of Syrian rebels.

Much more likely than rebel use in this case is inadvertent CW use by Syrian government forces. It is entirely possible that in the fog of war, a few CW shells were mixed up among conventional weapons or that an individual unit used CW without higher authority. Occam’s razor, the principle that the simplest theory is often correct, points to incompetence as a reason for use of CW in Syria. At least that possibility should be ruled out before any outside power intervenes militarily because of CW use.

This article was first published on the IISS Blog April 26, 2013.

Mark Fitzpatrick directs the IISS Non-Proliferation and Disarmament Program. Mr. Fitzpatrick's research focus includes nuclear proliferation concerns and preventing nuclear danger in the emerging ‘nuclear renaissance’. He is the author of The Iranian Nuclear Crisis: Avoiding worst-case outcomes (IISS Adelphi Paper 398, 2008) and has written articles on non-proliferation in the Financial Times, International Herald Tribune, Survival, and other publications.

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