Following his victory at the Battle of Pelagonia in 1259 AD against an anti-Nicaean coalition, the Nicaean emperor, Michael VIII Palaiologos, was left free to pursue the reconquest of Constantinople and the restoration of the Byzantine Empire.

[1] Already in 1260, Michael Palaiologos attacked Constantinople, as one of the Latin knights taken prisoner in Pelagonia, and whose house was within the city walls, had promised to open a gate for the emperor's troops.

[2][3] To further his plans, Michael concluded an alliance with Genoa in March 1261, and in July 1261, as the one-year truce following after the failed Nicaean attack was nearing its end, the general Alexios Strategopoulos was sent with a small advance force of 800 soldiers (most of them Cumans) to keep a watch on the Bulgarians and spy out the defences of the Latins.

[6] Strategopoulos initially hesitated to take advantage of the situation, fearing that his small force might be destroyed if the Latin army returned too soon, and because he would exceed the provisions of the emperor's orders, but eventually decided he could not squander such a golden opportunity to retake the city.

[8] The recapture of Constantinople signalled the restoration of the Byzantine Empire, and on 15 August, the day of the Dormition of the Theotokos, Emperor Michael VIII entered the city in triumph and was crowned at the Hagia Sophia.