The United States intelligence community has ''assessed'' that the Syrian government has used chemical weapons - probably the deadly nerve gas sarin - in its civil war against opponents of the Bashar al-Assad regime. The US is still being cautious in asserting its evidence to be conclusive, and so it (and Britain) should be after the weapons of mass destruction debacles of 12 years ago. But if the assessment is true, it marks a fresh stage in a civil war in which the regime has shown little restraint in using every other weapon said to be in its arsenal - including the use of artillery and missiles, as well as tank and aircraft strikes against civilian populations in cities. President Assad has been warned repeatedly that the deployment of any of Syria's reputed chemical warfare stocks would involve crossing a clear line in the sand, with the probable consequence of causing external intervention in the two-year-old civil war, which has already caused more than 70,000 civilian deaths and threatens to send millions of Syrians as refugees to nearby countries. Though the civil war has seen substantial secret aid to rebel groups from a number of countries, as well as substantial recruitment of rebel sympathisers, including from Australia, no nation has yet directly intervened in the struggle, or has an open channel of arms and military assistance to the rebels. The European Union, in particular, has an arms embargo on both sides of the conflict. Yet that the rebels are still in the fight, and with the plain sympathies of much of the Arab world, suggests substantial, if illicit, assistance.

Syria has vehemently denied the chemical warfare allegations, and Russia, whose veto power has so far protected Syria from United Nations action against Assad for his atrocities against his own population, has warned against any leap to conclusions about chemical warfare or any movement towards intervention. This advice is not detached, for Russia and Syria have long been military allies. But the need for the caution that it counsels is still obvious, if only because it is by no means clear what good purpose could be served either by external intervention, or by suddenly giving the rebels enough assistance to tip the balance in the conflict.

There is no single and united opposition group, and many of those who have taken up arms against Assad are fundamentalist extremists, some openly connected with or inspired by the al-Qaeda movement. As the war has progressed, rebels have seemed to become more and more dominated by anti-Western Islamists, with the more free and democratic outcome they claim to seek actually a theocratic dictatorship probably little less oppressive than the essentially secularist Assad regime. There is no doubt that the uprising was inspired by the Arab Spring in nations such as Tunisia, Libya and Egypt, and by the possibilities it suggested of the collapse of entrenched, oppressive and anti-democratic governments. It is, however, by now quite clear that a mere yearning for freedom, and for a right of participation in government, and genuine grievance against existing authorities, is not enough to guarantee Western-style secular democracies. As in Egypt, s