While reports of ISIS’ outright defeat in Iraq are dramatically overstated, there’s no denying that after over a year of heavy offensives, they’ve lost a lot of territory, and don’t constitute much of a de facto state there any longer. This is believed to be shifting ISIS’ focus to the west, into neighboring Syria.
The assumption is that this focus shift is a major reason why ISIS is so heavily committing to its ongoing offensive in the Deir Ezzor Province, where they’ve seized several districts of the capital city, and are trying to advance toward the key military airport in the area.
The airport on the outskirts of Deir Ezzor has long been seen as a huge strategic goal for ISIS, and has been attacked repeatedly, albeit unsuccessfully. It is the last military airport in eastern Syria which has never fallen to a rebel faction.
ISIS seems to be shifting away from territorial holdings in Iraq, and back toward a transitional insurgency, while in Syria they look to be trying to double down on protecting their territory, which is still substantial, and are likely to try to make pushes like the Deir Ezzor offensive to shore up their control over the eastern half of the country.