The Ottoman Crusade, known as the Grand Crusade, was the successful invasion of both the Ottoman Turkish lands in Anatolia, Greece and the Levant (the Holy Land), and the Circassian Turkish lands in Egypt and also the Levant, by a coalition of western European leaders in the early-to-mid fifteenth century. The crusade led to a radical restructuring of European politics, religion, culture and economics, and led to the resurgence of the Roman Empire in the east and the Kingdom of Jerusalem, and the resurrection and creation of various new crusader states stretching from Anatolia to the Red Sea. As well, the Catholic-Roman Orthodox Reconciliation in 1434 with the full conversion of John VIII and his leading vassals, ushered in a new era of Catholic supremacy.
Following various failed starts by Hungarian and Polish crusaders during the early part of the century, a successful crusade in Bohemia as well as the end of the Angevin-Valois Succession War, brought a renewed focus towards a pan-European Crusade. This was fully realised when Henry Beaufort assumed the Papal throne as Pope Leo X. Having fought in Bohemia, Leo X was a sympathetic ear to Emperor Sigismund.