Elizabeth Neumann spent March 13 and 14 of 2019 at a conference in the picturesque Spanish port city of Málaga. The topic: terrorism. Western leaders were deeply worried about the dangers foreign terrorist fighters traveling back from places like Iraq, Libya and Syria would pose to their home countries. And that’s what Neumann expected to dominate the two-day event.

Neumann was DHS’s assistant secretary for threat prevention and security policy at the time, handling counterterrorism work from the Department of Homeland Security’s headquarters. In Málaga, a history-drenched resort town on Spain’s Costa del Sol that once marked the fault line between the Muslim and Christian worlds, she and her counterparts from scores of countries spent long hours talking about the terrorism threats that concerned them most. After a while, she began to see a pattern: Though concerns about instability in the Middle East dominated most public discussions on counterterrorism, about 80 percent of the leaders at the conference ranked far-right extremism among their top concerns.

The next morning, when Neumann woke up early to catch a cab to […]