Sack of Thessalonica (904) participant Byzantine Empire
Background
The city, which is now in modern-day Greece, was in 904 A.D. a part of the Byzantine Empire, and was considered the greatest city in the empire, second only to Constantinople. Following the weakening of centralized power in the Abbasid Caliphate due to  the Fourth Fitna and the Anarchy at Samarra, many areas of the vast Abbasid Caliphate began to breakaway from the Caliph's control and while still paying religious lip service, acted independently on military and state matters.  The attention of these largely autonomous Muslim dynasties was subsequently turned to the Mediterranean sea. In 860 the Muslim dynasties attempted to reassert their dominance over the Mediterranean seaway and built naval bases at Tripoli and Tarsus. In 898, the eunuch admiral Raghib, a former mawla of al-Muwaffaq. decisively defeated a Byzantine fleet and carried off 3,000 Byzantine sailors of the Kibyrrhaiotai as prisoners. This naval battle proved to be a turning point as it opened the Aegean up to raids by the Muslim fleets.