Army Lt. Gen. Michael Nagata said Wednesday the Islamic State's threat to the U.S. and its allies will remain a significant threat long after the fall of Mosul and Raqqa.
"This is not a potential threat, this is a threat right now," he said, referring to ISIS militants going back to their home countries with the motive and inspiration to "go where you can, kill where you can."
"Just identifying the nature and scope of the problem is unfinished work today," said Nagata, head of the Directorate for Strategic Operational Planning at the National Counterterrorism Center.
In an address and question-and-answer session at the Center for Strategic and International Studies in Washington, D.C., Nagata echoed other estimates that about 40,000 foreign fighters from more than 100 countries -- "that's a breathtaking number" -- had rallied to the black flag of the Islamic State of Iraq and Syria to establish a caliphate in the Mideast.
He described the foreign fighters as "ethnically diverse, sociologically diverse" and drawn to ISIS for a variety of reasons.
"They are non-monolithic. Why do they do it? Some simply come for the adventure" and "some come to fight for ISIS for a variety of ideological reasons. Some come because they are seeking to address a grievance. I do not believe we know all of the motivations at this point."
The ranks of foreign fighters have been decimated by coalition airstrikes and advances by the Iraqi Security Forces and partnered local forces in Syria, Nagata said, but the threat from ISIS will remain as it evolves into a hit-and-run terrorist group once its fielded forces are defeated.
"The coalition is going to defeat the army of ISIS," but that will only exacerbate the threat of foreign fighters returning to their former homelands to spread havoc, he said.
"The most vivid challenge" faced by the international community will be the sharing of information and intelligence on the foreign fighters, Nagata said. Getting intelligence on the travel destinations of foreign fighters is "inherently difficult."
"We have to be patient," he said. "We are not going to end this threat this year. I don't think we can identify a time horizon. It will take years to solve this problem. If we try to pretend we can solve it sooner that, we are kidding ourselves."
At a White House news conference with President Donald Trump, Jordan's King Abdullah II made similar remarks about the foreign fighter threat. Foreign fighters disillusioned by ISIS' battlefield losses are "on the move beyond the region," Abdullah said. "How do we fight them? We have to understand how to deal with them globally."
Nagata said that stopping the cross-border movements of foreign fighters has been aided by passage of United Nations Resolution 2178 designating the travel -- or the assistance in the travel -- of foreign fighters as a criminal activity. The U.N. action has had a negligible effect, he said, but "just the fact that the world decided to make it a crime was an important step in the right direction."
Nagata previously, as head of special operations for U.S. Central Command, was in charge of the $500 million train-and-equip program aimed at setting up a moderate opposition in force in Syria.
However, those recruited for the program proved to be more intent on toppling the regime of Syrian President Bashar al-Assad than on fighting ISIS, which was the U.S. goal. The program produced only a few dozen of a promised 1,500 fighters and was canceled by the Obama administration in 2015.
-- Richard Sisk can be reached at Richard.Sisk@Military.com.