Sack of Constantinople (1204) in the context of "Reconquest of Constantinople"

Theodore Komnenos Doukas (Greek: Θεόδωρος Κομνηνὸς Δούκας, Theodōros Komnēnos Doukas; Latinized as Theodore Comnenus Ducas; died c. 1253) or Theodore Angelos Komnenos was the ruler of Epirus and Thessaly from 1215 to 1230 and of Thessalonica and most of Macedonia and western Thrace from 1224 to 1230. He was also the power behind the rule of his sons John and Demetrios over Thessalonica in 1237–1246.

Theodore was the scion of a distinguished Byzantine aristocratic family related to the imperial Komnenos, Doukas, and Angelos dynasties. Nevertheless, nothing is known about Theodore's life before the conquest of Constantinople and dissolution of the Byzantine Empire by the Fourth Crusade in 1204. Following the fall of Constantinople, he served Theodore I Laskaris, founder of the Empire of Nicaea, for a few years before being called to Epirus, where his half-brother Michael I Komnenos Doukas had founded an independent principality. When Michael died in 1215, Theodore sidelined his brother's underage and illegitimate son Michael II and assumed the governance of the Epirote state. Theodore continued his brother's policy of territorial expansion. Allied with Serbia, he expanded into Macedonia, threatening the Latin Kingdom of Thessalonica. The capture of the Latin Emperor Peter II of Courtenay in 1217 opened the way to the gradual envelopment of Thessalonica, culminating in the city's fall in 1224.

The Latin Patriarchate of Constantinople was an office established as a result of the Fourth Crusade and its conquest of Constantinople in 1204. It was a Catholic replacement for the Eastern Orthodox Ecumenical Patriarchate of Constantinople and remained in the city until the reconquest of Constantinople by the Byzantines in 1261, whereupon it became a titular see with only ceremonial powers. The St. Peter's Basilica was the patriarchium, or papal major basilica assigned to the Patriarch of Constantinople, where he officiated when visiting Rome. The office was abolished in 1964.