Struggle for Constantinople in the context of "Alexios V Doukas"

The Despotate of Epirus (Medieval Greek: Δεσποτᾶτον τῆς Ἠπείρου) was one of the Greek rump states of the Byzantine Empire established in the aftermath of the Fourth Crusade in 1204 by a branch of the Angelos dynasty. It claimed to be the legitimate successor of the Byzantine Empire during the subsequent struggle for Constantinople, along with the Empire of Nicaea and the Empire of Trebizond; its rulers briefly proclaiming themselves as Emperors in 1227–1242 (during which it is most often called the Empire of Thessalonica). The term "Despotate of Epirus" is, like "Byzantine Empire" itself, a modern historiographic convention and not a name in use at the time.

The Despotate was centred on the region of Epirus, encompassing also Albania and the western portion of Greek Macedonia and also included Thessaly and western Greece as far south as Nafpaktos. Through a policy of aggressive expansion under Theodore Komnenos Doukas the Despotate of Epirus also briefly came to incorporate central Macedonia, with the establishment of the Empire of Thessalonica in 1224, and Thrace as far east as Didymoteicho and Adrianople, and was on the verge of recapturing Constantinople and restoring the Byzantine Empire before the Battle of Klokotnitsa in 1230 where he was defeated by the Bulgarian Empire. After that, the Epirote state contracted to its core in Epirus and Thessaly, and was forced into vassalage to other regional powers. It nevertheless managed to retain its autonomy until being conquered by the restored Palaiologan Byzantine Empire in ca. 1337. In the 1410s, Carlo I Tocco, Count Palatine of Cephalonia and Zakynthos, managed to reunite the core of the Epirote state, but his successors gradually lost it to the advancing Ottoman Empire, with the last stronghold, Vonitsa, falling to the Ottomans in 1479.

The Empire of Thessalonica is a historiographic term used by some modern scholars to refer to the short-lived Byzantine Greek state centred on the city of Thessalonica between 1224 and 1246 (sensu stricto until 1242) and ruled by the Komnenodoukas dynasty of Epirus. At the time of its establishment during the struggle for Constantinople, the Empire of Thessalonica, under the capable Theodore Komnenos Doukas, rivaled the Empire of Nicaea and the Second Bulgarian Empire as the strongest state in the region, and aspired to capturing Constantinople, putting an end to the Latin Empire, and restoring the Byzantine Empire that had been extinguished in 1204.

Thessalonica's ascendancy was brief, ending with the disastrous Battle of Klokotnitsa against Bulgaria in 1230, where Theodore Komnenos Doukas was captured. Reduced to a Bulgarian vassal, Theodore's brother and successor Manuel Komnenos Doukas was unable to prevent the loss of most of his brother's conquests in Macedonia and Thrace, while the original nucleus of the state, Epirus, broke free under Michael II Komnenos Doukas. Theodore recovered Thessalonica in 1237, installing his son John Komnenos Doukas, and after him Demetrios Angelos Doukas, as rulers of the city, while Manuel, with Nicaean support, seized Thessaly. The rulers of Thessalonica bore the imperial title from 1225/7 until 1242, when they were forced to renounce it and recognize the suzerainty of the rival Empire of Nicaea. The Komnenodoukai continued to rule as Despots of Thessalonica for four more years after that, but in 1246 the city was annexed by Nicaea.