十字軍國家
The conquest of Constantinople was followed by the fragmentation of the Byzantine Empire into three states centered in Nicaea, Trebizond and Epirus. The Crusaders then founded several new Crusader states, known as "Frankokratia", in former Byzantine territory, largely hinged upon the Latin Empire of Constantinople. The presence of the Latin Crusader states almost immediately led to war with the Byzantine successor states and with the Bulgarian Empire. The Nicaean Empire eventually recovered Constantinople and restored the Byzantine Empire in 1261.