The migration waves of Byzantine scholars and émigrés in the period following the Crusader sacking of Constantinople in 1204 and the end of the Byzantine Empire in 1453, is considered by many scholars key to the revival of Greek and Roman studies that led to the development of the Renaissance humanism, and science. These émigrés brought to Western Europe the relatively well-preserved remnants and accumulated knowledge of their own (Greek) civilization, which had mostly not survived the Early Middle Ages in the West. According to the "Encyclopædia Britannica": "Many modern scholars also agree that the exodus of Greeks to Italy as a result of this event marked the end of the Middle Ages and the beginning of the Renaissance".