200 ships towards the end of Andronikos I's reign. Elsewhere Isaac's policy was less successful. In late 1185, he sent a fleet of 80 galleys to liberate his brother Alexius III from Acre, but the fleet was destroyed by the Normans of Sicily. He then sent a fleet of 70 ships, but it failed to recover Cyprus from the rebellious noble Isaac Komnenos, thanks to Norman interference. This fleet was misinterpreted by many in the Holy Land as naval support for the Muslim offensive in accordance with Isaac's alliance with Saladin. However the theory of a supposed alliance between Isaac and Saladin against the Third Crusade has been debunked by the historian Jonathan Harris. Isaac's administration was dominated by two figures: his maternal uncle Theodore Kastamonites, who became virtually a co-emperor and handled all civil government until his death in 1193; and his replacement, Constantine Mesopotamites, who acquired even more influence over the emperor. The oppressiveness of his taxes, increased to pay his armies and finance his marriage, resulted in a Vlach-Bulgarian uprising late in 1185. The rebellion led to the establishment of the Vlach-Bulgarian Empire under the Asen dynasty. In 1187 Alexios Branas, the victor over the Normans, was sent against the Bulgarians but turned his arms against his master and attempted to seize Constantinople, only to be defeated and slain by Isaac's brother-in-law Conrad of Montferrat. Also in 1187 an agreement was made with Venice, in which the Venetian Republic would provide between 40 and 100 galleys at six months' notice in exchange for favorable trading concessions. Because each Venetian galley was manned by 140 oarsmen, there were about 18,000 Venetians still in the Empire even after Manuel I's arrests. The Emperor's attention was next demanded in the east, where several claimants to the throne successively rose and fell. In 1189 the Holy Roman Emperor Frederick I Barbarossa sought and obtained permission to lead his troops on the Third Crusade through the Byzantine Empire. But Isaac was suspicious that Barbarossa wished to conquer Byzantium: the reasons for this suspicious attitude were the diplomatic contact of Frederick with the Bulgarians and the Serbians, foes of the Byzantine Empire during this period, also Barbarossa's previous feud with Manuel. The rumors of 1160s about a German invasion in the Byzantine Empire were still remembered in the Byzantine court during Isaac’s reign. In retaliation Barbarossa's army occupied the city of Philippopolis and