Two years into Washington's war against the Islamic State group, it may finally be winning. At the same time, however, its influence over events in the broader Middle East seems perhaps terminally in decline.

What happens in the coming months and years in Syria will be key to the future shape of the region. No country has challenged U.S. policymakers more — and the Obama administration has faced heavy criticism. This month, however, has seen what feels like the first good news for the United States from Syria since the uprising began.

In early August, U.S.-backed Syrian forces seized back the town of Manbij. Footage of jubilant locals embracing those they see as liberators has been flashed around the globe, providing exactly the kind of propaganda victory Washington needed.