This alternate timeline deals with the Byzantine Empire surviving to the present day under the Palaiologos dynasty. Note that most of history outside the eastern Mediterraenean is basically the same as in real life.
Pope Eugene IV calls for a Crusade against the Ottomans in January. In October, a Christian alliance attacks the Ottomans, including:
- Papal States
- Teutonic Order
- Bulgarian rebels
The allies were led by the King of Poland and Hungary, Wladyslaw III and also by John Hunyadi and the Sebian despot Durad Brankovic. Sultan Murad II was leading the Ottoman troops.
The crusaders caught the Turks by surprise and quickly advanced through Bulgaria. In early December, the Ottomans mounted a counter-offensive and forced the crusaders to retreat. The Christians, however, used the weather and terrain to their advantage and ambushed the pursuing Ottoman army in the so-called Dragoman pass in Bulgaria, where the Ottomans suffered a crushing defeat. Murad II was killed in the ensuing battle and the crusaders had a clear path into the Ottoman lands. In most parts of Bulgaria, Greece and other Balkan territories they were welcomed as liberators. They halted their advance at the Bosporous strait, not willing to advance into Asia Minor for the time being.
The question of what to do with the reconquered territories emerged. Some in the Catholic Church preferred recreating of the Latin Empire, which was non-existent for almost two hundred years now. The Hungarians and Poles would instead prefer to add at least some of the territory to their respective kingdoms. However, before the alliance leaders could decide on something, the local rebels took the initiative. Parts of Romanian lands occupied by the Ottomans proclaimed themselves to be part of Wallachia or Moldavia. Part of the territory was taken by Serbs which proclaimed Durad Brankovic as their new king. A new Bulgarian Empire was also proclaimed by the local rebels.
Ioannes VIII, the Byzantine Emperor, watched the events of the crusade carefully and was delighted when he learned of the crusaders' victory. Several minor Greek revolts erupted in cities and Constantine, the Emperor's brother, who was Despot of Morea at the time, assembled his men and easily retook the former Despotate of Epirus together with the area around Thessaloniki.