The first great city the crusaders came to in 1089 was not Jerusalem but Constantinople, the capital of the Byzantine empire. Almost as much as Jerusalem itself, Constantinople was the key to the foundation, survival and ulti-mate eclipse of the crusading kingdom.

The Byzantines had developed an ideology over seven hundred years which placed Constantinople rather than Rome or Jerusalem at the centre of the world. The attitudes of its rulers reflected this priority, and led to tensions with the cru-saders over military and diplomatic strat-egy At the same time, the riches and sophistication of the great city made a lasting impression on the crusaders, even though they found Byzantine society alien and remote. Tn the end, the lure of the city's wealth was irresistibly fatal to the claims of Christian unity In 1204 the Fourth Crusade, under the Venetian doge Enrico Dandolo, captured and sacked Constantinople, signalling the effective end of almost a thousand years of Byzantine dominance in the east.