It's the latest development in the U.S. military's struggle to bring to justice the man charged with planning the Sept. 11 attacks on the United States.
U.S forces are still needed in Syria to prevent ISIS from reconstituting as a major threat following Assad's ouster, Defense Secretary Lloyd Austin said.
The piecemeal progress of extremism-prevention efforts during the past four years is more than can be expected out of the Pentagon in 2025, experts said.