For anyone who thought that the winding down of the campaign against ISIS would cause the Syrian civil war to recede from the headlines, the last few weeks have been a rude awakening. Far from abating, the Syrian conflict is intensifying, with a brutal assault -- reportedly involving chemical weapons -- by the Syrian regime on rebel-held areas near Damascus, sharp aerial clashes between Israeli, Iranian and Syrian forces, and a bloody and one-sided confrontation between American airpower and Russian "mercenaries." These events do more than simply demonstrate that the Syrian conflict remains an appalling humanitarian catastrophe. More significantly, Syria is the nexus for the destabilizing trends that are thrusting the entire global order into crisis. That order was originally created after World War II, but it reached its full flowering and ambition after the fall of the Soviet Union. The post-Cold War era was characterized by widespread hopes that the forces of order and civilization were finally defeating those of aggression and inhumanity; that democracy was becoming truly universal; that great-power competition had vanished; and that the danger of major war was receding further than ever before. Nearly three decades later, however, the heady optimism of that period has given way to a darker set of trends, all of which are at work in Syria. Syria is where the erosion is most advanced and the consequences most horrific. The regimes continued use of starvation sieges, barrel bombs and illegal weapons against the civilian population -- and the international communitys inability or unwillingness to bring the slaughter to an end -- demonstrates more painfully than anything else that the moral gains the world seemed to have achieved are now being rolled back, and the rules of conduct it seemed to have established are now being transgressed. Neither the Barack Obama administration, with its "red-line" fiasco of 2013, nor the Donald Trump administration, with its diplomatic disengagement from the conflict, has had an answer to this challenge. The Syrian war also reveals a second unsettling feature of global politics today: the return of ideological conflict. This is not to say that the civil war is a clash between entrenched authoritarians and aspiring democrats. Many Syrians who initially protested and fought against the regime in 2011 and 2012 wanted a transition to a more pluralistic system, but most of those moderates have now been killed, radicalized or otherwise driven from the field. Nonetheless, the Syrian conflict reflects the broader authoritarian resurgence at work. Head of Syrian regime Bashar al-Assad offers a brutal and ruthless example. Moreover, the war shows how ideological differences are again driving global politics. Most of the Western democracies have insisted -- rhetorically, at least--that the killing must stop and Assad must go. Yet the worlds leading autocracies have rejected the idea of foreign-imposed regime change and provided various forms of assistance to keep a fellow autocrat in power. The competition between authoritarianism and democracy has been renewed, and nowhere has that competition been sharper than in Syria. Meanwhile, intense geopolitical competition has also returned, and here too, Syria is ground zero. Iran and Israel are maneuvering -- often violently -- for advantage, as part of their broader regional struggle. More strikingly still, Syria has become an arena for renewed great-power rivalry between the US and Russia. The once and current adversaries do not simply disagree over Assads fate; they are using their military power to carve out competing spheres of influence and stake their respective claims to leadership. Russia in particular is using Syria as a proving ground for the advanced weapons systems and hybrid-warfare tactics it might well employ in a future conflict with the West, as well as to make itself a player in Middle Eastern geopolitics. Bloomberg