Not So Long Ago...

The following is an excerpt from the excellent book, The New Concise History of the Crusades:

After Orkhan's death in 1360, the Ottomans began their European conquests in earnest. In 1361, they captured most of Thrace, including Adrianople, which became their capital in the West. By the end of the fourteenth century, they controlled all of Bulgaria and most of Greece. Constantinople itself was completely surrounded — a citizen could leave the empire simply by walking outside the city gates.

The rise of the Ottoman Turks and their successful campaigns to the West dramatically changed the stakes in the crusading movement. It was no longer faraway Palestine that was in danger but western Europe itself. Crusaders had always seen themselves as fighting a defensive war, defending the Christians in the East, Jerusalem, or the faith. Now they were called on to defend themselves. Henceforth, crusades were no longer wars to expand Christendom (to reinstate its existence after Christendom had been largely overrun by Islamic hordes) but desperate attempts to slow the advance of Islam (into Europe). Crusading had become a matter of simple survival.

The destruction of the Crusade of Nicopolis was a devastating defeat for western Europe. Hungary lay virtually defenseless before the sultan's armies, and beyond that was the German Empire. For the first time, Europeans began to consider seriously what life would be like under Turkish occupation, in a world in which there were no Christian states.

Read more about the Crusades.