Andronikos IV resented his father's acceptance of tributary and vassal status to the Ottoman Empire in 1373, and in the same year, he joined Savcı Bey, a son of the Ottoman Sultan Murad I, in a joint open rebellion against their fathers.[5] Both revolts were suppressed, although Byzantine military weakness meant that this was largely carried out by Turkish troops.[4] Murad blinded (and later executed) Savcı and demanded that John V in turn blind both Andronikos and the latter's son, John, as well. John V did so only partially, leaving Andronikos IV with one eye and his grandson only partially blinded, but he did imprison Andronikos.[2] The younger John greatly resented his grandfather's action and would rebel against him in 1390, reigning for five months.[6] In the aftermath of Andronikos' failure, Manuel was raised to co-emperor and heir to John V as Manuel II.