When, in our turbulent day, we hear of a “clash of civilizations,” it’s easy to imagine an unbridgeable chasm between the Islamic world and Christendom stretching back through time. But such assumptions crumble before the drama that unfolds in this book. Two Faiths, One Banner shows how in Europe, the heart of the West, Muslims and Christians were often comrades-in-arms, repeatedly forming alliances to wage war against their own faiths and peoples.

Here we read of savage battles, deadly sieges, and acts of individual heroism; of Arab troops rallying by the thousands to the banner of a Christian emperor outside the walls of Verona; of Spanish Muslims standing shoulder to shoulder with their Christian Catalan neighbors in opposition to Castilians; of Greeks and Turks forming a steadfast bulwark against Serbs and Bulgarians, their mutual enemy; of tens of thousands of Hungarian Protestants assisting the Ottomans in their implacable and terrifying march on Christian Vienna; and finally of Englishman and Turk falling side by side in the killing fields of the Crimea.

This bold book reveals how the idea of a “Christian Europe” long opposed by a “Muslim non-Europe” grossly misrepresents the facts of a rich, complex, and—above all—shared history. The motivations for these interfaith alliances were dictated by shifting diplomacies, pragmatic self-interest, realpolitik, and even genuine mutual affection, not by jihad or religious war. This insight has profound ramifications for our understanding of global politics and current affairs, as well as of religious history and the future shape of Europe.