Map of the Byzantine Successor States 1218 AD

The death of Manuel Komnenos in 1180 exposed the improvised nature of the Komnenian revival and ushered in a new period of instability and weakness, culminating in the disaster wrought by the 4th Crusade in 1204. This early exercise in western commercial and military imperialism led to the conquest and partial destruction of Constantinople. A new so-called "Latin Empire" was established upon the ruins of Byzantium, whilst Byzantine refugees established fragmented successor states in Northern Greece and Asia Minor, each claiming the the Byzantine inheritance.

The Empire of Nicaea emerged as the most viable successor state and was to go on to recapture Constantinople in 1261.