The retreat of the Byzantine army from Syria in around 650 CE, in advance of the approaching Arab armies, is one that has resounded emphatically in the works of both Islamic and Christian writers, and created an enduring motif: that of the Islamic-Byzantine frontier. For centuries, Byzantine and Islamic scholars have evocatively sketched a contested border: the annual raids between the two, the line of fortified fortresses defending Islamic lands, the no-man s land in between and the birth of jihad. In their early representations of a Muslim-Christian encounter, accounts of the...