For a thousand years after the fall of the West, the empire of Byzantium, centred on the great city of Constantinople, perpetuated the living, unbroken legacy of the Roman empire. It reached the peak of its latter-day power in 1025 under the Emperor Basil II, but a dozen weak and corrupt successors squandered his accomplishments until the very existence of the empire was under threat. In these circumstances, a dynamic, young leader named Alexios Komnenos rose to the imperial throne from a cabal of the powerful military families, and through hard-fought campaigns and cunning diplomacy managed to reassert the strength and glory of Byzantium. But he was not unopposed: Turks, Normans, Bulgarians, Germans and Venetians constantly pressed at his borders, while contenders from within his own and rival families schemed recklessly to usurp his throne. With the Turks in particular advancing ever further into the hinterland of Asia Minor, Alexios was forced to beg the estranged Pope in Rome to provide soldiers to buttress the faltering Byzantine armies. Much to his surprise, and subsequent alarm, he got them: the Pope preached the first crusade, and tens of thousands of western knights mobilised to descend on Byzantium.
The language of Byzantium was Greek, but through all its history its citizens referred to themselves as Romans. Any peoples beyond the empire’s borders were considered barbarians.