The jihadist group swept across Syria and Iraq the same year, declaring a cross-border “caliphate” in territory roughly the size of Britain, attracting thousands of foreign fighters.
But several military offensives, including those backed by the US-led coalition, have since seen IS lose most areas it once controlled.
“More than 7.5 million people have now been liberated from ISIS,” McGurk said in a statement, adding that the group’s finances are now “at their lowest levels to date”.
With the jihadists’ dreams of statehood lying in tatters following the battlefield defeats, Western attention is increasingly pivoting to trying to block foreign fighters from returning home to carry out attacks.
McGurk insisted that flows of foreign IS fighters into Syria have “nearly stopped”, and that jihadists are increasingly being picked up as they cross borders.
“We are enhancing cooperation and border security, aviation security, law enforcement, financial sanctions, counter-messaging, and intelligence sharing to prevent ISIS from carrying out attacks in our homelands,” he said.