The Byzantine Empire, religiously separated from Rome since 1054, and disappeared for the first time after the sack of Constantinople by the Crusaders (1204), is in full decline:the Palaiologos dynasty, in power since 1258 and whose last representative is Constantine Dragases (1449-1453), no longer controls a reduced and fragmented territory, most of which is formed by Constantinople.
The Ottoman Empire, on the contrary, formed at the end of the 15th century and made up of Turks who had arrived in Anatolia two centuries earlier, emerged from a difficult period:at the end of the 16th century, its expansion towards the east is found blocked by the will of a terrible conqueror, also Turkish:Timur Lang (1370-1405), founder of an immense and ephemeral empire in Central Asia. After the death of Timur Lang, the Ottoman sultans, Mehmed Ie, Murad Il and especially Mehmed ll, nicknamed the Conqueror (1444-14? and 1451-1481), can consider conquests again, and turn in particular to the Balkans .