The
Massacre of the Latins, a massacre of the
Roman Catholic or "
Latin" inhabitants of
Constantinople by the usurper
Andronikos Komnenos and his supporters in May 1182, affected political relations between Western Europe and the
Byzantine Empire and led to the
1185 sack of Thessalonica by Normans. Although regular trade agreements were soon resumed between
Byzantine and Latin States, some Westerners sought some form of revenge. Venetian merchants had carefully mapped Constantinople's harbours years before the sack, possibly anticipating its economic potential.
Alexios IV Angelos, the son of deposed emperor
Isaac II Angelos persuaded Boniface of Montferrat and the Venetians to help him reinstate his father and make him co-emperor of the Byzantines by diverting the Fourth Crusade to Constantinople. In return, he promised 200,000 marks of silver as payment, as well as the submission of the Eastern Orthodox Church to Rome. Additionally he promised to pay for the provisions of the expedition and to join the crusade against the Saracens. Following the
siege of Constantinople in 1203, on 1 August 1203 the pro-Crusader
Alexios Angelos was crowned Emperor Alexios IV of the Byzantine Empire. He attempted to pacify the city, but riots between anti-Crusader Greeks and pro-Crusader Latins broke out later that month and lasted until November, during which time most of the populace began to turn against him. On 25 January 1204, the death of co-Emperor
Isaac II set off rioting in Constantinople in which the people deposed
Alexios IV. He turned to the Crusaders for help, but was imprisoned by the imperial chamberlain,
Alexios Doukas, who declared himself Emperor on 5 February, before executing Alexios IV by strangulation on 8 February. Alexios V then attempted to negotiate with the Crusaders for a withdrawal from Byzantine territory without payment, but they refused in order to avenge Alexios IV and receive the money that was promised. == Siege: first assault ==