The US, mirroring similar claims from the UK and France, has asserted that the government of Bashar al Assad has used chemical weapons (CW) in Syria, specifically the nerve agent sarin. As a consequence, the US will now provide military assistance to the anti-Assad rebels.
Given the gravity of this claim and its consequences, as well as a recent history of unevidenced assertions based on inaccurate intelligence being used to justify involvement in foreign wars, how does the evidence in the latest assertion stack up?
The CW claim has two components, each of which must be considered separately. The first is that CW have been used; the second that they have been used by Assad's government.
In respect of the first component, the US has referred to apparently compelling evidence. Videos by news reporters and opposition activists, the reports of doctors, as well as forensic testing of samples and the bodies of rebel fighters all suggest the use of a nerve agent such as sarin, as does that casualties reportedly responded positively to atropine - a nerve agent antidote.
Of course, such evidence can be part of an elaborate fabrication. On balance however it seems possible, at least to this onetime chemical warfare trained writer, that sarin has indeed been used.
One must therefore move on to consider the second component of the US claim, that not only has sarin been used, but that it has been used by Assad's forces. It is in this respect, at least publicly so far, that the US has produced little if any evidence to support its claim, other than to suggest that as the rebels don't have sarin, its use must therefore have been by Assad. This assumption however may be false.
For example, just two weeks ago security forces in neighbouring Iraq announced the capture of an alleged al Qaeda cell engaged in the manufacture of sarin. The al Nusra Front, long reported to be at the core of the most effective anti Assad Syria rebel forces, is integrally linked to the same al Qaeda group to which the alleged Iraqi terrorists belong.
Similarly, in neighbouring Turkey the week before, police arrested a number of Syrian al Nusra suspects, reported by the Turkish media to be in possession of sarin. Turkey is a strong supporter of Syria's rebels however, and the sarin story quickly disappeared from the Turkish media - just as also happened recently to coverage of Turkey's current anti-government protests.
To this picture must be added the comments of Carla del Ponte, a leading member of the UN Commission of Inquiry (CoI) into the alleged use of CW in Syria. The commission has yet to report, but on 6 May del Ponte, a former war crimes prosecutor, stated that there was strong evidence of the use of sarin by Syria rebels.
There is then, contrary to the US claims, ample evidence to suggest that Syria's rebels have access to sarin, or the capability to produce or acquire it. Obama himself implicitly acknowledged this in his "red line" speech of August 2012, when he stated that the red line was intended not only for Assad, but for the rebels too - suggesting his intelligence services considered this a credible possibility.
Further, in assessing any crime, one must consider not only the capabilities of the different parties, but also their motives. Yet this crucial evidential aspect has been publicly ignored by the US, UK and France, and by the media of these countries in their often uncritical reporting of their claims.
Following Obama's red-line speech, Assad and his commanders have known that any CW use would invite US intervention on the rebel side. Yet such use, particularly on the small scale alleged by the US, would bring little if any tactical advantage over and above the use of Assad's considerable array of conventional weapons. It seems unlikely, almost inconceivable, therefore that he would risk massive US intervention for such little, if any, military gain.
This situation is reversed however for the rebels, who ever since Obama's red line was created have had every incentive to use CW, which could then be blamed on Assad to provoke US intervention. Indeed, as even the pro-opposition Syrian Observatory for Human Rights pointed out in January, rebels have frequently made claims of Syria government use of CW, but these claims are never confirmed as true.
For anti-rebel activists such a turn of events, a so-called "false flag" operation, has long been predicted, as for example in this activist video. For such activists, as for surely anyone looking objectively at the evidence made public so far, there are strong grounds to at least suspect that this prediction may now have come true.
It's of course no coincidence that the sudden US decision that Assad has used CW, and to consequently assist Syria's rebels despite grave concerns as to who the rebels are and what the consequences for US interests and the people of Syria might be, has come just days after the serious reversal of rebel fortunes at Qusair. In the last few days, Obama has come under intense pressure from France, the UK and his own media to save the retreating rebels, whether to blindly show US resolve, or to simply bloody the nose of Iran. Perhaps even more compelling as an explanation is that just days ago the Syrian opposition refused to attend Obama brokered peace talks unless he supplied them with US weapons. In this context, the CW issue would be a useful pretext to justify rather than explain deeper US involvement, just as WMD were used by the US and UK ten years ago to justify the Iraq war.
If this is the case, and intelligence has again been used, with or without Obama's knowledge, to fabricate a pretext for US overseas military intervention, there will be dismay among those who claim the lessons of Iraq haven't been learned. For others however, it will confirm the suspicion that lessons have indeed been learned - that without any negative consequences for themselves, governments supported by their intelligence services and media remain able to make unevidenced assertions as a pretext for otherwise largely unjustifiable overseas military adventures and interventions.