defeated a Byzantine army of 3,000 men that attempted to recapture the city. The Byzantine troops managed to constantly and successfully harass the Crusaders but a group of Armenians revealed to the Germans the strategic plan of the Byzantines. The Crusaders, who outnumbered the Byzantines, caught them unprepared and defeated them. Thus compelled by force of arms, Isaac II was forced to fulfill his engagements in 1190, when he released imprisoned German emissaries who were held in Constantinople, and exchanged hostages with Barbarossa, as a guarantee that the crusaders would not sack local settlements until they departed the Byzantine territory. In March 1190, Barbarossa left Adrianople to Gallipoli at the Dardanelles to embark to Asia Minor. By 1196, Isaac II had allowed the once powerful Byzantine navy to decline to only 30 galleys. The next five years were disturbed by continued warfare with Bulgaria, against which Isaac led several expeditions in person. In spite of their promising start these ventures had little effect, and on one occasion in 1190 Isaac barely escaped with his life. The Byzantines suffered yet another major defeat in the Battle of Arcadiopolis in 1194. Isaac organized yet another offensive against Bulgaria in 1195 in cooperation with the Kingdom of Hungary, but Alexios Angelos, the Emperor's older brother, taking advantage of Isaac's absence from camp on a hunting expedition, proclaimed himself emperor and was readily recognised by the soldiers as Emperor Alexios III on 8 (or 9) April. Alexios then canceled the expedition and ordered Isaac to be blinded and imprisoned in Constantinople. Second reign After eight years of captivity, Isaac II was raised from the dungeon to the throne once more after the arrival of the Fourth Crusade and the flight of Alexios III from the capital. Both his mind and body had been enfeebled by confinement, and his son Alexios IV Angelos was associated on the throne as the effective monarch. Heavily beholden to the crusaders, Alexios IV was unable to meet his obligations and his vacillation caused him to lose the support of both his crusader allies and his subjects. At the end of January 1204 the influential court official Alexios Doukas Mourtzouphlos took advantage of riots in the capital to imprison Alexios IV and seize the throne as Alexios V. At this point Isaac II died, allegedly of shock, while Alexios IV was strangled. Usurpers Several pretenders rose up and attempted to