While many of the thousands of foreign fighters who flocked to Syria and Iraq died on the battlefield or were captured, significant numbers have managed to return to their home countries—or, in some cases, moved to other battlefields.

Indeed, while Islamic State’s ability to produce slick propaganda has been degraded by the loss of a physical “state,” the extremist group still retains a robust online presence and successfully encourages so-called lone-wolf attacks.

In one of these, a stabbing spree in central Paris, a young Frenchman of Chechen origin Saturday killed a passerby and injured four others after recording a cellphone video pledging allegiance to Islamic State. A series of much bloodier suicide attacks on Sunday, also claimed by Islamic State, targeted churches in Surabaya, Indonesia.

“Although Islamic State’s ideology has suffered, it still has a huge potential,” said Rohan Gunaratna, head of the International Center for Political Violence and Terrorism Research at the Nanyang University in Singapore. “Islamic State has entered a phase of global expansion, very much the same way al Qaeda extended globally in late 2001.”