The Sack of Thessalonica in 904 by the Abbasid Caliphate's navy was one of the worst disasters to befall the Byzantine Empire during the reign of Leo VI and even in the 10th century. A Muslim fleet of 54 ships, led by the renegade Leo of Tripoli, who was a recent convert to Islam, set sail from Syria with the imperial capital of Constantinople as its initial target. The Muslims were deterred from attacking Constantinople, and instead turned to Thessalonica, totally surprising the Byzantines, whose navy was unable to react in time. The Abbasid raiders appeared and after a short siege lasting less than four days, the attackers were able to storm the seaward walls, overcome the Thessalonians' resistance, and take the city on 29 July. The sacking continued for a full week before the raiders departed for their bases in the Levant, having freed 4,000 Muslim prisoners while capturing 60 ships, gaining a large amount of loot and 22,000 captives, mostly young people, and destroying 60 Byzantine ships in the process.