“The estimates of how many fighters terror groups, such as ISIS, have are always a complex endeavor,” senior director of the Counter Extremism Project, Hans-Jakob Schindler, tells the New York Sun. “One of the key challenges is what is classified as a ‘fighter’. Some governments only estimate the number of individuals that are armed and involved in actual fighting or attacks, while other governments also count all the supporters, including, for example, families.”

Counter Extremism Project (CEP) Senior Research Analyst Sofia Koller discusses the foreign terrorist fighter situation and camps in Syria and Iraq. [Starting at 06:29]

[Counter Extremism Project Senior Director] Hans-Jakob Schindler, a former UN Security Council co-ordinator for monitoring ISIS and Al Qaeda, said ISIS has sensed that "this is our opportunity to come back". He said the group's willingness to declare a "new phase" of operations hinted at a boost to manpower after the prison escapes and a push to recruit from Mr Al Shara's ranks.

Following serious riots at a Kurdish demonstration in Dortmund, terrorism expert [CEP Senior Director] Hans-Jakob Schindler warns against importing the Syrian conflict to Germany. Schindler also fears an uncontrolled return of German IS fighters from Syria.

Terrorism expert Hans-Jakob Schindler of the transatlantic think tank Counter Extremism Project says that the interim president relies on foreign jihadists to stabilize his rule and does not want to appear within the Islamist spectrum as someone who betrays former comrades-in-arms.

Although the United States, under all administrations, has continued to conduct attacks against ISIS positions, the recent killing of the three Americans in Syria explains the intensification of U.S. operations. “It’s essentially about showing ISIS that if it carries out attacks against American interests, it must understand that there will be very serious consequences,” comments Hans-Jakob Schindler, director of the Counter Extremism Project in Berlin.