With no regular American presence in the war theater, the US has struggled to answer basic intelligence questions about the situation in Syria and Iraq, including the Islamic State group's fighting strength.
The drone strikes, separate from the large air campaign run by US Central Command, have significantly diminished the threat from the Khorasan Group, an al-Qaeda cell in Syria that had planned attacks on American aviation, officials say.
Intelligence analysts and special operators have harnessed an array of satellites, sensors, drones and other technology to find and kill elusive militants across a vast, rugged area of Syria and Iraq, despite the lack of a ground presence and steps taken by US targets to disguise their use of electronic devices.
The CIA's Counter Terrorism Center brought its collection and analytical expertise to the hunt for senior militants in close cooperation with JSOC, officials say, with a new focus on achieving a hybrid model that has long been the Obama administration's goal.
