U.S. Marine artillerymen are now in place on Syrian soil, north of the last stronghold of the Islamic State. A force of local Kurdish and Arab fighters is moving south, continuing to isolate the city of Raqqa.
They're in the opening stages of a major military operation that officials say could last into the fall.
What comes next is expected to have huge implications not only for the fate of ISIS but also for the relationship between Turkey and Russia, as well as the geographic outlines of the future Syrian state.
It will be very complicated.