Any use of chemical weapons is barbaric. But the case for intervention in Syria remains weak

The images are truly horrendous. Dozens of bodies laid out in rows, many of them children; dozens more people, including very young children again, are seen suffering spasms – the classic results, so it would appear, of a major gas attack. Appalling though the pictures are, however, is all as clear cut as it seems? The photos and video have been circulated by Syrian opposition activists; the timing of their release, as UN experts arrived in Syria to investigate the reported use of chemical weapons, has powerful propaganda value.

But would any leader – even one as beleaguered and brutal in defence of his power as President Bashar al-Assad – be so heedless of the consequences as to launch such an attack just as the UN inspectors came to call? Mr Assad has denied it – but he would, wouldn’t he? Anyway, the alternative is even less plausible: that the rebels staged, exaggerated or manipulated an attack on areas they hold east of Damascus with the intention of swaying both the inspectors and international opinion towards intervention. A third option, hazarded by some, is that the dead and injured were exposed not to nerve gas, but to tear gas in a confined space. But we are talking degrees here, rather than the principle – the barbaric lengths to which a desperate regime will go to keep power.

The response of most international leaders has so far been, quite rightly, outrage, hedged – also rightly – with a measure of caution. “If proven” is the crucial qualifier to the calls from Britain, France and others for action. It is also a pointer to the priority: which must be to establish, so far as possible, the truth of what happened. To that end, the UN experts now in Syria must be granted access to the area of the alleged atrocity. This appears unlikely. But if Mr Assad is as confident as he purports to be that government forces were not responsible, this is his chance.

Establishing the truth is essential in order to pre-empt yet another mealy-mouthed response from the UN Security Council. But it is essential, too, because the stakes are so high. The use of chemical weapons in the Syrian conflict was defined as a “red line” by President Obama a year ago, when he said that if the Assad regime deployed chemical weapons, “the whole calculus would change”. This was widely interpreted as a condition for the US to intervene, either directly or by arming the rebels. Nor can it be excluded that the rebels thus divined a way in which they might force the US hand. So far, an EU investigation has found only small-scale use of sarin gas on both sides. Such an extensive attack as seems to have taken place this week, if found to be the work of Mr Assad’s forces, could not but “change the calculus”.

But would it, and should it, prompt Western intervention? There are, of course, levels of intervention, from air strikes targeting arsenals to boots on the ground, and the rebels already receive some help. As we know from Afghanistan and Iraq, however, even limited intervention tends to produce perverse results and here it could be even riskier, given Syria’s complexity and its ever more volatile neighbourhood.Direct intervention may one day seem less perilous than doing nothing, but even now the case has not been made.