For Western Europe, the Crusades were a grand adventure whose function was largely to give younger siblings among the nobility something to do besides plot against their firstborn brothers. But for the Byzantine Empire, on Christendom’s frontier with the Islamic world, the Crusades were chiefly a logistical nightmare. Apart from pissing off the Turks and Arabs, whom the Byzantines would have to continue living next to after the Franks, Germans, et al. had gone home, the Crusades involved huge numbers of soldiers marching across the breadth of the empire’s territory, spoiling for action and pillaging the countryside for food and plunder. Emperor Alexius I’s primary aim in 1096, when the first Crusaders arrived, was to keep them fed and keep them moving until they were out of his dominions and could vent their bloodlust on someone other than his subjects. In his lecture, “The Byzantine Background to the First Crusade,” Paul Magdalino of the Department of Medieval History, St. Andrews University, will probably address these issues, although his take on the subject may be a little unorthodox, since the press release mentions (in what one hopes is a typo) the empire’s efforts at cultural unification in the 1970s. See if he means it at 5:30 p.m. at Dumbarton Oaks’ Music Room, 1703 32nd St. NW. FREE. (202) 339-6410. CP