Numerous competent studies have appeared on Christian apologetics—both Byzantine and Western Medieval—against Islam. A significant gap, however, remains. The Byzantines, of course, first encountered Islam because of the Arab conquest in the second and third quarters of the seventh century. Yet the earliest known Byzantine apologist against Islam is Saint John Damascene in the eighth century. But what initial impression did the Arab conquest and Islam make upon seventh-century Byzantine contemporaries? The seventh-century Byzantine sources on Byzantine reactions to the Arab conquest are scarce, inconveniently located, and insufficiently studied. There is no known individual Byzantine tract of the seventh century devoted specifically to the problem of Islam and/or the Arab conquest. But even though seventh-century sources are relatively rare—on any subject—by a close reading of those which are available one can glean some interesting and, in my opinion, important indications concerning Byzantine reactions to the Arab conquest. Obviously such a major historical event as the loss of Egypt, Palestine and Syria would greatly have impressed the Byzantines and would have caused them to ponder its significance.