The nation-state is undoubtedly the most important political formation in modern world history. It is universally recognized and aspired to, but not universally realized. The nation is never a finished project, and nationalism, which is understood here as the cultural politics that has the nation as its subject and its object, derives its energy and motivating force from perceived threats from within and without. While nationalism is a modern phenomenon, religion is often regarded as either ancient or transcending history. Before the nineteenth century, religion everywhere in the world was an integral part of statecraft. The legitimation of rulers came from heaven and was mediated by priestly and monastic classes. This is true in Christendom, but also in other major religions like Islam, Hinduism, Buddhism, Confucianism, and Shintoism.