Tell me about Constantine XI

[Sarmatian]

The Byzantine empire was doomed when they lost Anatolia at the battle of Manzikert. Anatolia was the cultural and economic guts of the Byzantines, and the Seljuks ripped those guts out. The Ottomans just administered the coup de grace to the twitching corpse of Byzantium.

I wouldn't quite agree. Loss of Anatolia was a severe blow, undoubtebly, but Byzantium had a history of recovering after devastating defeats. In my opinion, gradual shift from centralised bureacracy to more feudal like ruling system was the chief cause of byzantium downfall because it ruined the military system of the empire. But if had to put my finger on a single event that harmed Byzantium the most, the 1204 sacking of Constantinople would be my pick...