After his coronation he carried on three successful campaigns against the Saracens and Seljuk Turks, whom he drove beyond the Euphrates; in a fourth he was disastrously defeated by Alp Arslan in 1071 on the banks of the Araxes at the Battle of Manzikert and taken prisoner.
After releasing himself by the promise of a large ransom and the conclusion of a peace, he turned his arms against the pretender Michael VII, but was compelled after a defeat to resign the empire and retire to the island of Prote, where he soon died in great misery.
It was during this reign that, by the surrender of Bari to the Normans in 1071, the Byzantine Empire lost its last hold upon Italy.
Based on an entry from the 1911 Encyclopedia Britannica.
Michael VII (co-emperor)