The Ottoman Turks had expanded their empire…

The Ottoman Turks had expanded their empire from Anatolia to the Balkans in the fourteenth century.

They had crossed the Bosporus in 1352, and in 1389 they had crushed a Serb-led army that included Albanian forces at Kosovo Polje, located in the southern part of present-day Kosovo.

Europe gains a brief respite from Ottoman pressure in 1402 when the Mongol leader, Tamerlane, at- tacks Anatolia from the east, kills the Turks' absolute ruler, the sultan, and sparks a civil war.

When order is restored, the Ottomans renew their westward progress.

In 1453 Sultan Mehmed II's forces overrun Constantinople and kill the last East Roman emperor.