In nearly every conflict in which I've been involved, foreign fighters have played a significant and dangerous role. These disparate groups and individuals have grown to be a permanent fixture of modern extremist movements, and are tied irrevocably to unresolved sources of radicalization, the power of jihadi narratives, the emergence of social media, and the ease of international travel. Byman has captured all of this in one book, which I wish had been available to other commanders and me a generation ago as America first began to grapple with the horrific reality of global terrorism. He has done us all a great service, and I commend this excellent book in the strongest possible terms.
Daniel Byman is a Professor at Georgetown University's School of Foreign Service and a Senior Fellow at the Center for Middle East Policy at the Brookings Institution.