Yet as the chaos spread, the Obama Administration had a good reason to resist involvement: Obama was elected as the anti-Bush, with no mandate clearer than staying out of messy conflicts in the Middle East. In doing so, the administration has missed the opportunity to build ties — and the political careers — of moderate elements in the rebellion, and is increasingly hostage to the fear of who will replace Assad once he falls.

Sitting on the sidelines of the Middle Sast for two years has had its effect.

“The structure of US alliances in the region has completely changed,” said Ayham Kamel, a Beirut-based analyst for Eurasia Group. “You have an environment where there are no back channels to resolving issues in the region.”

On Thursday, Obama travels to Russia for a summit of the G20 nations. The meeting was always going to be tense, coming at a time when US-Russia relations stand at a post-Cold War low. Now the world will be watching its results with intense interest. One question: Will Putin use the gathering as a means of trying to humiliate Obama or will he indicate some desire to put pressure on Assad — assuming, and many US diplomats privately don’t, that he has that power?