According to tradition, the First Crusade began at Pope Urban II's instigation and culminated in July 1099, when western European knights liberated Jerusalem. But what if the First Crusade's real catalyst lay far to the east of Rome? Countering nearly a millennium of scholarship, Peter Frankopan reveals the First Crusade's untold history in the person of Alexios I Komnenos of Constantinople, emperor of the Christain Byzantine Empire.