The Sack of Thessalonica in 1185 by Normans of the Kingdom of Sicily was one of the worst disasters to befall the Byzantine Empire in the 12th century. The city's governor, David Komnenos, had neglected to make sufficient preparations for the siege, and even forbade sallies by the defenders to disrupt the Norman siege works. The Byzantine relief armies failed to coordinate their efforts, and only two forces, under Theodore Choumnos and John Maurozomes, actually came to the city's aid. In the event, the Normans undermined the city's eastern wall, opening a breach through which they entered the city. The conquest degenerated quickly into a full-scale massacre of the city's inhabitants, some 7,000 corpses being found afterwards. The siege is extensively chronicled by the city's archbishop, Eustathius of Thessalonica, who was present in the city during and after the siege. The Normans occupied Thessalonica until mid-November, when, following their defeat at the Battle of Demetritzes, they evacuated it. Coming on the heels of the Byzantine massacre of the Latins in Constantinople in 1182, the massacre of the Thessalonians by the Normans deepened the rift between the Orthodox Byzantine Greeks and the Catholic Latins (Western Europeans). As a demonstration of the Byzantine Empire's military feebleness, it also directly led to the deposition of the unpopular and tyrannical Andronikos I Komnenos and the rise to the throne of Isaac II Angelos, a fact that raises many questions considering the sub-standard defense of the city by governor David Komnenos, member also of the wider Komnenian family just like Isaak II Angelos.