The participation of Alexios Doukas Mourtzouphlos in the attempted overthrow of
Alexios III Angelos () by
John Komnenos the Fat in 1200 had led to his imprisonment. Mourtzouphlos was probably imprisoned from 1201 until the restoration to the throne of
Isaac II Angelos (), the brother and predecessor of Alexios III. Isaac II, along with his son Alexios IV Angelos, were restored to the throne through the intervention of the leaders of the
Fourth Crusade in July 1203. On release, Mourtzouphlos was invested with the court position of
protovestiarios (head of the imperial finances). He had been married twice but was allegedly the lover of
Eudokia Angelina, a daughter of Alexios III. By the beginning of 1204, Isaac II and Alexios IV had inspired little confidence among the people of
Constantinople with their efforts to protect the city from the
Latin crusaders and their
Venetian allies, and the citizens were becoming restless. The crusaders were also losing patience with the emperors; they rioted and set fires in the city when the money and aid promised by Alexios IV was not forthcoming. The fires affected about a sixth of the area of Constantinople and may have made up to a third of the population homeless; the dislocation and desperation of those affected eventually sapped the will of the people to resist the crusaders. Alexios Doukas Mourtzouphlos emerged as a leader of the anti-Latin movement in the city. He won the approval of the populace by his valour in leading an attack on the Latins at "Trypetos Lithos"; in this clash his mount stumbled and he would have been killed or captured had a band of youthful archers from the city not defended him. Mourtzouphlos exploited the hatred of the people for the Latins to serve his personal ambition. The citizens of Constantinople rebelled in late January 1204, and in the chaos an otherwise obscure nobleman named
Nicholas Kanabos was acclaimed emperor, though he was unwilling to accept the crown. The two co-emperors barricaded themselves in the
Palace of Blachernae and entrusted Mourtzouphlos with a mission to seek help from the crusaders, or at least they informed him of their intentions. Instead of contacting the crusaders, Mourtzouphlos, on the night of 28–29 January 1204, used his access to the palace to bribe the "ax-bearers" (the
Varangian Guard), and with their backing arrest the emperors. Choniates states that Mourtzouphlos, when bribing the guards, had the help of a eunuch with access to the imperial treasury. The support of the Varangians seems to have been of major importance in the success of the coup, though Mourtzouphlos also had help from his relations and associates. The young Alexios IV was eventually strangled in prison; while his father Isaac, both enfeebled and blind, died at around the time of the coup, his death variously attributed to fright, sorrow, or mistreatment. Kanabos was initially spared and offered an office under Alexios V, but he refused both this and a further summons from the emperor and took sanctuary in the
Hagia Sophia; he was forcibly removed and killed on the steps of the cathedral. ==Emperor==