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.
Background The stated goal of the Sicilian expedition, sent by William II of Sicily, was to replace Andronikos Komnenos with a Byzantine pretender who was claiming to be the deposed Alexios II.Magdalino, P. (2008). The empire of the Komnenoi (1118–1204). In J. Shepard (Ed.), The Cambridge history of the Byzantine Empire c. 500–1492 (pp. 627–663). Cambridge University Press. This was in retaliation to the Byzantine Emperor destabilizing his dynasty in Sicily.Holmes, C. (2019). De-centring 12th-century Constantinople: Archbishop Eustathios and the Norman conquest of Thessalonica revisited. In Byzantium and the West (pp. 142-155). Routledge. William had also supported Isaac Komnenos of Cyprus before this.Bird, J. (2025). Aftermath in the East (and West) of the Third Crusade. In The Third Crusade (1189–1192) (pp. 193–213). De Gruyter Brill.
Some sources also report that William II was motivated by an alleged incident in which Manuel Komnenos had humiliated William. In the incident, William accepted a proposal to marry Manuel's daughter Maria, but the union was never realized in the last moment, likely because Frederick I offered the Byzantine Emperor a better deal.Tounta, E. (2022). Political and Cultural Encounters between Byzantium and the Normans, 11th-12th Centuries. A Companion to Byzantium and the West, 900-1204. Wiliam was humiliated by fruitlessly waiting in Taranto for his wife to arrive for days.Thomas, E. (2010). 'We have nothing more valuable in our treasury': royal marriage in England, 1154-1272 (Doctoral dissertation, University of St Andrews).Stone, A. F. (2003). The Oration by Eustathios of Thessaloniki for Agnes of France: A Snapshot of Political Tension between Byzantium and the West. Byzantion, 73(1), 112-126.
Siege David Komnenos, the governor, had failed to prepare for the siege and banned defenders from disrupting Norman siege works, hindering the city's defense. 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. They slaughtered the defenders and proceeded to sack the city. The conquest degenerated quickly into a full-scale massacre of the city's inhabitants, with estimates suggesting that around 7,000 to 8,000 corpses were 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.
Aftermath The Normans occupied Thessalonica until mid-November, when, following their defeat at the Battle of Demetritzes, they evacuated it. After emperor Andronikos Komnenos's massacre of the Latins in Constantinople in 1182, the massacre of the Thessalonians deepened the rift between Western Christianity and Eastern Christianity. It also directly led to the deposition and execution of the unpopular Emperor Andronikos and the rise to the throne of Isaac II Angelos.
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λεηλάτησης της Θεσσαλονίκης