From the tenth century on, Constantinople began to find her rivalries in the west. The coronation of Charlemagne in 800 had marked the final separation of the eastern and the western empire. As noted above, the passing of the Saracens gave opportunity for the growth of commercial city-states like Genoa, Pisa and Venice, and their interests clashed not only with one another but also with those of Constantinople.
The climax came in 1204 when Venice succeeded in diverting the Fourth Crusade to an expedition of vengeance for herself, first against the city of Zara and then against Constantinople. This time the Eastern Empire had no fleet ready for defense and the Venetian galleys filled the waters under the city walls. Many of these galleys were fitted with a kind of flying bridge, a long yard that extended from the mast to the top of the wall and stout enough to bear a file of men that scrambled by this means to the parapets. After many bloody repulses the city was finally captured, and there followed a sack that for utter barbarity outdid anything ever perpetrated by Arab or Turk. Thus the city that for nearly a thousand years had saved Christian civilization was, by a hideous irony of fate, taken and sacked by a Crusading army.
When the second Mohammedan invasion threatened Europe, Constantinople, weak on land and impotent by sea, and deserted by the Christian nations of the west, was unable to put up a strong resistance. At last, in 1453, it was captured by the Turks, and became thereafter the capital of the Moslem power. Great as this catastrophe was, it cannot compare with what would have happened if the city had fallen to the Saracen, the Hun, or the Russian during the dark centuries when the nations of the west were scarcely in embryo. In the 15th century they were strong enough to take up the sword that Constantinople had dropped and draw the line beyond which the Turk was not permitted to go.
Although it has been the fashion since Gibbon to sneer at the Eastern Empire, it must be remembered with respect as the last treasure house of the inheritance bequeathed by Rome and Greece during the dark centuries of barbarian and Saracen. Even in its ruin it sent its fugitives westward with the manuscripts of a language and literature then little known, the Greek, and thereby added greatly to the growing impetus of the Renaissance. It is significant also that during its thousand years of life, as long as it kept its hold on the sea it stood firm. When it yielded that, its empire dwindled to a mere city fortress whose doom was assured long before it fell.
REFERENCES
Cambridge Medieval History, Vol. II., 1913.
The History of the Saracens, E. Gibbon & S. Ockley.
History of the Decline and Fall of the Roman Empire, Edward Gibbon, ed. by J. B. Bury.
The Byzantine Empire, E. A. Foord, 1911.
Military and Religious Life in the Middle Ages, Paul Lacroix, 1874.