When it comes to the deradicalization of foreign terrorist fighters in modern Western societies, the Frisians—meaning here the present-day regions of Ostfriesland and Land Wursten in Germany, and the provinces of Friesland and Groningen in the Netherlands—have neither a strong track record nor notable expertise to offer. Their only meaningful contribution to contemporary counterterrorism efforts lies in the lessons of their own past: a vivid example of how radicalization and