This collection of essays on international hybrid threats and proper responses is a veritable cornucopia of empirical research findings and analytic insights, in the manner of so much good research and writing coming out of Sweden on matters of war and peace. With a wide array of authors from the world’s democracies, the contributions in this volume will be attractive to professionals and the public alike who are interested in the gray zone falling between outright war and peace in this trouble world---the space that Russia likes to operate within, for example, as Moscow attempts to manipulate Western opinion and undermine the open societies. One of the volume’s great strengths is its melding of thinking on this subject by both scholars and practitioners. Fascinating, too, are a series of case studies included among the chapters, with probes into hybrid threats and warfare as seen from the perspectives of China, Iran, Russia, the United States, and several other illustrations. The relevance, thoughtfulness, and practicality of this book cannot be overstated.