Manuel II and respite from the Turks
The loss of Thessalonica and the Battle of Kossovo sealed off Constantinople by land. The new sultan Bayezid I (1389–1402) intended to make it his capital; when Manuel II Palaeologus came to that throne at his father’s death in 1391, the Sultan warned him that he was emperor only inside the city walls. The Turks already controlled the rest of Byzantine Europe, except for the south of Greece.
In 1393 Bayezid completed his conquest of Bulgaria, and soon afterward he laid siege to Constantinople. The blockade was to last for many years. Manuel II, like his father, pinned his hopes of rescue on the West. A great Crusade against the Turks was organized by the King of Hungary, but it was defeated at Nicopolis on the Danube in 1396.
In 1399 the French marshal Boucicaut, who had been at Nicopolis and had returned to the relief of Constantinople with a small army, persuaded Manuel to travel to western Europe to put the Byzantine case in person. From the end of 1399 to June 1403 the Emperor visited in Italy, France, and England, leaving his nephew John VII in charge of Constantinople. Manuel’s journey did something to stimulate Western interest in Greek learning. His friend and ambassador in the West, Manuel Chrysoloras, a pupil of Demetrius Cydones, were appointed to teach Greek at Florence.
The Pope instituted a defense fund for Constantinople. Interest and sympathy were forthcoming but little in the way of practical help. During Manuel’s absence, however, the Ottomans were defeated at Ankara by the Mongol leader Timur (Tamerlane) in July 1402. Bayezid was captured and his empire in Asia was shattered.
His four sons contended with each other to secure possession of the European provinces, which had been little affected by the Mongol invasion, and to reunite the Ottoman dominions. In these wholly unexpected circumstances the Byzantines found themselves the favoured allies first of one Turkish contender, then of another. The blockade of Constantinople was lifted.
Thessalonica—with Mount Athos and other places—was restored to Byzantine rule, and the payment of tribute to the sultan was annulled. In 1413 Mehmed I, helped and promoted by the emperor Manuel, triumphed over his rivals and became sultan of the reintegrated Ottoman Empire.