In 1259, the Empire of Nicaea, led by Michael VIII Palaiologos (r. 1259–1282), had achieved a great victory in the Battle of Pelagonia against a coalition of its major European foes, the Despotate of Epirus, the Kingdom of Sicily, and the Principality of Achaia.

[1] This victory enabled Palaiologos to consolidate his territories in Europe; further, the weakening of Epirus and the Latin states allowed him to carry out the reconquest of Constantinople in 1261 and to re-establish the Byzantine Empire, with himself as emperor.

[2] The Nicaean forces failed however to subdue Epirus: John Doukas quickly returned to his father's allegiance, and the local population remained loyal to Michael II.

Nevertheless, Michael VIII tried to attach them to him through dynastic marriages: Nikephoros was given his niece Anna Kantakouzene, while one of his nephews, Andronikos Tarchaneiotes, was wed to the daughter of John Doukas, who in addition received the light title of sebastokrator.

[6] Nevertheless, through the negotiations, the Act of Union and the submission of the Greek Orthodox Church to the See of Rome, Michael averted the danger of a concerted Latin attack on his state, and was free to move against his enemies.

[8] Doukas was caught completely by surprise by the rapid advance of the imperial forces, and was bottled up with few men in his capital, Neopatras, which the Byzantines proceeded to lay siege to.

[16] Deno J. Geanakoplos placed the Thessalian campaign after the Council of Lyon, hence in late 1274 or early 1275,[17] and his dating has been adopted by a number of recent scholars like Donald Nicol and John Van Antwerp Fine.