The conflict was inevitable, as ISIS has already taken materially the entire Deir Ezzor Province of Syria under their control. Today they looked to take that last major piece, the Syrian military airport.

The air base is not only it as far as territory in Deir Ezzor outside of ISIS hands, but is also Syria’s government’s last major airport in the nation’s east, from which strikes along the Iraq border have come.

ISIS has been slowly seizing the villages around the airport for weeks, and has been expelling rivals from what little territory they had left in the province, a major oil producing region.

The first clashes were reported today outside the airport, as ISIS tried to force its way in through the front gate. By evening the indications are that Syria still holds the airport, but history suggests ISIS will siege it for days or weeks if necessary to get what it wants, and with the airport so far out of Assad government territory, keeping it is going to be next to impossible in the face of a protracted siege.

Deir Ezzor is thought to have the largest oil reserves of any Syrian province, and between it and ISIS’ other possessions they are believed to have about 60% of Syria’s production capacity under their direct control now.