Isaac II (Isaac Angelus), d. 1204, Byzantine emperor (1185-95, 1203-4). The great grandson of Alexius I, he was proclaimed emperor by the mob that had killed the unpopular Andronicus I. Isaac repulsed (1185) an invasion by the Normans under William II of Sicily but was unable to suppress the rebellious Bulgars. Corruption in public office continued during his reign. He was deposed and blinded in 1195 by his brother, who became emperor as Alexius III, but Isaac's son (later Alexius IV) appealed to the Latins of the Fourth Crusade (see Crusades), and in 1203 father and son were restored as coemperors. Their overthrow (1204) by Alexius Ducas (Alexius V) led to the storming of Constantinople by the Crusaders.