Demetrios Angelos Doukas (), was ruler of Thessalonica with the title of Despot as a vassal of the Empire of Nicaea from 1244 until his deposition in 1246. Origin Born , Demetrios was the younger son of Theodore Komnenos Doukas and Maria Petraliphaina. As such he was a great-grandson of the Byzantine emperor Alexios I Komnenos () and Empress Irene Doukaina, and first cousin once removed of the emperors Isaac II Angelos () and Alexios III Angelos (), sharing descent from Constantine Angelos, the founder of the Angelos lineage. Unlike his father and most of his relatives, who eschewed the surname of "Angelos" due to the disastrous reigns of the Angelid emperors, and preferred to use the more prestigious surnames of "Doukas" or "Komnenos", Demetrios used the name "Angelos Doukas" (Ἀγγελοδούκας) in a manuscript notice dated 25 September 1244. Background His father Theodore ruled over the Byzantine successor state of Epirus since 1215, and after the conquest of the Latin Kingdom of Thessalonica in 1224, had founded the Empire of Thessalonica, in rivalry with the other major Byzantine successor state, the Empire of Nicaea in western Asia Minor. By 1230, he seemed poised to recover Constantinople from the Latin Empire and thus restore the Byzantine Empire, but in that year he was defeated and captured at the Battle of Klokotnitsa by Ivan Asen II of Bulgaria, and was blinded after being implicated in a plot against Ivan Asen. In the aftermath of Klokotnitsa, Theodore's empire collapsed: within a few months most of Thrace, Macedonia, and Albania, fell under Bulgarian rule. Theodore's brother Manuel, who managed to escape from Klokotnitsa, now took over the throne in Thessalonica, ruling over a much-reduced domain as a vassal of the Bulgarian ruler. When his sister Irene married Ivan Asen in 1237, Theodore was released from captivity. Theodore made his way back to Thessalonica and overthrew Manuel, but as he was blind, he installed his oldest son John as emperor. In 1244, however, the Nicaean emperor John III Doukas Vatatzes campaigned against Thessalonica, and forced John to recognize his suzerainty and renounce his imperial title, receiving the title of Despot instead. Rule of Thessalonica Theodore himself retired to Vodena, from where he supervised the affairs of state. On John's death in 1244 Demetrios succeeded his brother as ruler of Thessalonica (sometime before 25 September 1244). An embassy was to Nicaea to announce the succession, as