Iskander Rehman is an Ax:son Johnson Fellow at the Henry A. Kissinger Center for Global Affairs. He holds a Ph.D. with distinction from the Institute of Political Studies (Sciences Po) in Paris, and can be followed on Twitter @IskanderRehman. An adapted version of this introduction to Polybius will feature in the forthcoming Classics of Applied History: Lessons of the Past (Stockholm, Sweden: Bokförlaget Stolpe, 2022) edited by John Bew, Andrew Ehrhardt and Mattias Hesserus.