Isaac II Angelos

Isaac II Angelos led a popular revolt that overthrew Andronikos I Komnenos, and was proclaimed emperor. His accession ended the Komnenian dynasty's rule and began the Angelid dynasty, but the empire was weakened by internal strife and external threats.

Isaac II led a campaign against the Bulgarian rebels under Ivan Asen I and Peter IV. The Byzantine army was ambushed and defeated at Tryavna, with Isaac barely escaping. The defeat solidified the Second Bulgarian Empire's independence from Byzantine rule.

Isaac II was overthrown and blinded by his brother Alexios III Angelos in a palace coup. Isaac was imprisoned, and Alexios III seized the throne. The blinding was a traditional Byzantine punishment for usurpers, but it left Isaac incapacitated and the empire divided.

Isaac II was restored to the throne by the Fourth Crusade, alongside his son Alexios IV Angelos, after the crusaders besieged Constantinople. However, the restored regime failed to pay the promised rewards to the crusaders, leading to renewed conflict and Isaac's death in prison in 1204.