Book excerpt: 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. "Two Faiths, One Banner" shows how in Europe, Muslims and Christians were often comrades-in-arms, repeatedly forming alliances to wage war against their own faiths and peoples. 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.