Manuel I Comnenus (ca. 1123-1180) was Byzantine emperor from 1143 to 1180. Although he was a talented ruler, his diplomatic and military overextensions left his realm dangerously isolated and humiliated.

The fourth son of John II Comnenus (1118-1143), Manuel was the second one surviving at the time of his father's death in a "hunting accident" that was probably an assassination. Supposedly by the dying John's wish, Manuel was given the throne in preference to his older brother. Manuel assembled a dazzling and lavish court and presided over one of the most brilliant phases of Byzantine culture. He was also an able soldier, strategist, and commander. Nevertheless, his perception seems to have been at times superficial, and his policies, although imaginative, were often misguided.

Manuel's basic policies were to recover the lands in Asia Minor lost to the Turks, to assert control over the crusader states of the Holy Land, to...