Violence is often called the “dark underbelly” of religion—and indeed, it invariably accompanies all religious traditions of the world, from the era of archaic sacrifices to 21st-century jihadism. But why, if all religions talk about love, peace and universal harmony, do they fight endless wars? With this question, Mark Juergensmeyer went to radical Christians in the United States and Northern Ireland, Jewish zealots, architects of the intifadas in Palestine and refugees from the Middle East, Sikh activists in India and Buddhist activists in Myanmar and Japan. The result is this book, the most authoritative study to date on religious terror and the relationship between religion and violence in general. The key to this connection, the author states, is the idea of “cosmic warfare,” which refers to both the eternal struggle between light and darkness and the underworld wars waged by believers of all the world’s religions against those they perceive as enemies. Images of war and sacrifice smolder deep within every religious tradition, ready to transform from symbol to reality, with globalization, political ambitions, and the historical destinies of the 20th and 21st centuries adding fuel to this fire. Mark Juergensmeyer is Professor Emeritus of Sociology and Global Studies at the University of California, Santa Barbara.