Beats Me

11.06.14 7:25 PM ET

ISIS Has 9,000 ‘Core Fighters.’ Or Maybe 17,000. Or Possibly 30,000.

Another day, another American estimate of ISIS’s strength that’s vastly different from the last guess.

How many fighters are the U.S. and its allies combatting in its new war against ISIS? American military and intelligence leaders have only the vaguest of notions. Estimates of ISIS’s strength from these leaders have varied wildly, and now the military commander in charge of degrading and destroying the extremist group says it could be as low as just 9,000 “core fighters.”

Gen. Lloyd Austin’s estimates of ISIL’s numbers ranged from a low of 9,000 to a high of nearly double that figure—17,000. The CIA had previously estimated up to 30,000 fighters in ISIS’s ranks.

The truth is that the United States lacks the intelligence to form a trustworthy estimate of the group’s strength. Austin’s low estimate is just a third of what the CIA suggested their numbers could be, just a few short months ago.

“That number has bounced around a bit,” Austin acknowledged. “Without having the human intelligence on the ground to confirm or deny, it’s very difficult.”

And the CENTCOM commander said that ISIS figures could expand dramatically based on the nature of its actions. 

“If it rolls through the Sunni population and generates a bunch of local support, those numbers can quickly swell,” Austin told a packed room at the Atlantic Council in Washington Thursday.

Austin also characterized the anti-ISIS campaign currently being led by the United States as more focused on Iraq than Syria, even though there have been more airstrikes in Syria lately—and even though the extremist group operates on both sides of the border.

“We’re focused on Iraq as our main effort. What we’re doing in Syria is really designed to shape the efforts in Iraq,” Austin said, in response to Free Syrian Army criticism that the coalition isn’t doing enough to coordinate with them.

ISIS still holds major cities on both sides of the border: Raqqa, Mosul, and Fallujah, to name a few. But Austin insisted that the coalition has had success during its operation—which he stressed is as much about disrupting the bad guys as it is killing them—by interrupting their ability to communicate privately, move freely between Iraq and Syria, and raise funds (through attacking ISIS’s mobile refining and crude collection capability).

“They’re afraid to congregate in any sizable formation, because they know if we can see them, we’re going to engage them and we’re going to hit where we’re aiming at. They have extreme difficulty communicating on a day to day basis,” the four-star general said. “It’s getting increasingly difficult for [ISIS fighters] to sustain themselves with fuel, refined products… we’re seeing this on a daily basis.”

The campaign to destroy ISIS will ultimately take years, not decades, Austin told the crowd. But one of the reasons why the group has been so resilient, he said, was its skill in utilizing propaganda.

“This adversary is about as good as I’ve ever seen,” he said. “A number of the folks that are in the ranks of this organization have been in this business before. So they’ve learned the lessons of Iraq and other places, and they really understand the value of trying to dominate the media space.”