to the west to beg for help. He was rewarded with only sporadic reaction. Only the threat to Constantinople itself finally galvanized the west, which sent a huge and splendid expedition with John, son of the duke of Burgundy, at its head. When this ended in fiasco at Nicopolis ( 1396) the west appeared to lose heart totally. No further forces against the Turks were sent until a similar venture met its end at Varna in 1444. That Constantinople held out until the mid-fifteenth century was due more to the unexpected respite caused by the sudden advance into Asia Minor of the Mongol Timur, who defeated and captured Bajezid in 1402. Already in the late fourteenth century it was left largely to the Serbs to defend Europe and Christendom against the Ottomans. The Byzantines, who had by now become Turkish vassals, were so impotent that they were but waiting for the end. What vigour there was among the Greeks centred on the regained territory of the Peloponnese, based on Mistra, where the late Byzantine cultural revival, a splendid flowering in the face of political adversity, found its main focus.
The Ottomans by contrast were assuming the characteristics of an organized state. The Balkan acquisitions were colonized, the subjected people assimilated, taxed, and drawn on for troops. Some of that territory had been yielded readily. As well as the stick of their terrifying military prowess, the carrot of superior organization and stability and of religious tolerance made them attractive to many by comparison with the divided and ineffective rule of the Byzantines. The real impact of the Ottoman advance came in the next century as the threat spread to include western possessions in the east and even the Italian mainland. But the basis for the Muslim hold on Europe was laid in the fourteenth century, and the Mediterranean was already beginning to feel the consequences.
The appearance of crisis is also present in the development of the Spanish kingdoms in the period. The rapid absorption of so much territory in the reconquest of the early thirteenth century brought its particular problems. At the same time the Spanish kingdoms became increasingly involved in the international political scene, in the Mediterranean and on the northern
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