Discreet Russian support has long helped keep Bashar al-Assad in power. Now the Kremlin is intervening overtly, with advisers, the fortification and expansion of air bases, and even T-90 tanks, according to American officials—presumably in preparation for heavy reinforcements. Russia is also suggesting a joint effort, with the American-led coalition, to fight Islamic State. Help can’t come soon enough for Mr Assad. Rebel groups captured an important air base on September 9th and hilltops near the capital, Damascus, on September 12th. What is Vladimir Putin up to? One explanation is that, piqued by Western snubs, he wants to show (not least to his own people) that Russia is still an indispensable superpower. Another is that he wants to make the West, beset by worries over migrants, accept that Mr Assad should stay. Both could be true. What Russia’s president wants may become clear on September 27th, when he makes a speech at the UN General Assembly.