WEAKENING OF THE EMPIRE BY ATTACKS FROM THE NORTH.
IN order to understand how it came to pass that during the last century and a half before the Latin Conquest the Empire was almost continually receiving attacks from the North, it is necessary to recall what was the position of the capital in regard to the populations of the Balkan peninsula. As the frontier guard of Europe, Constantinople had had constantly to fight frontier battles against the races of Asia in their march westward. During many centuries a great forward movement of these races had been going on along the north shores of the Black Sea, and when the twelfth century closed this movement had not altogether ceased.
Constantinople, as I have already said, during the rule of the Byzantine emperors, had been like an island amid a sea of peoples. On its north, its west, and its south, hardly a generation had passed without some great change in the masses of people who had been submitted to its rule. Neither the people of Constantinople nor the bulk of the inhabitants of the Balkan peninsula were of Greek origin. The efforts of comparative philologists have not yet conclusively decided how to classify the Epirots, the Thracians, and even the inhabitants of Macedonia. What is certain is that to this day the Balkan peninsula is strewn with wrecks of races which represent successive waves of population that have flowed into Europe from Asia. The shores and the islands of the Ægean were inhabited in Byzantine times, as they are now, by people of Greek origin. The Illyrians, whose descendants are the present Northern Albanians, occupied parts of Dalmatia,
Remains of many races in Balkan peninsula.