Without God on Our Side

IN THE FOURTH century, the Roman emperor Constantine laid the foundations for a remarkably durable venture. This was the spread of Christian empire. Constantine’s own empire would divide into Eastern and Western halves, from which multiple Christian empires emerged. One was Byzantium, and another was the Holy Roman Empire. Later European empires were legion: the Spanish, the Portuguese, the French, the Russian, the Austro-Hungarian, and the British empire, with its many claims on modern geopolitics. “Christianity is an inherently expansive faith,” Andrew Preston writes, and this faith has often accompanied imperial expansion. Church and empire were inclined to march together. Or so it must have seemed in Europe until World War I—“Christendom’s ultimate civil war,” in Preston’s words.