On the division of the Roman Empire, Greece fell of course to the
eastern or Byzantine half. In 1204 the Crusaders and Venetians captured
Constantinople, and divided the Empire--an act which has been taken as
the end of “the Byzantine Empire.” Baldwin, Count of Flanders, was
elected Emperor of Roumania, and reigned at Constantinople. Many new
states sprang out of the partition, and new empires were founded at
Nicæa, Trebizond, and Thessalonica. The feudal system was established in
Greece. Athens became a fief of Roumania, governed by dukes; a great
part of the Peloponnesus was kept first by Franks and then by
Neapolitans, as the Principality of Achæa. The Venetians obtained
possession of most of the islands.
Of all the confused and crowded events of these times probably the most
important, was the capture of Constantinople in 1261 by Michael
Palæologus, Emperor of Nicæa, but no attempt to hold Greece could long
endure in the face of the Ottoman Turks who soon began to threaten from
the East. In 1453 the Sultan Mohammed II. took Constantinople. The
Venetians finally surrendered all claim to most of their Greek
possessions by the Treaty of Passarowitz in 1718.