Constantine X - Basileus of Basileía Rhōmaíōn from 1159 to 1167
Constantine X was emperor of the Byzantine Empire from 24 November 1059 to 22 May 1067.

The new emperor quickly included two of his young sons with the throne, appointed his brother John Doukas as kaisar (Caesar), and embarked on a policy favorable to the interests of the court bureaucracy and the church. Severely undercutting the training and financial support for the armed forces, Constantine X fatally weakened Byzantine defences by disbanding the Armenian local militia of 50,000 men at a crucial point of time, coinciding with the westward advance of the Seljuk Turks and their Turcoman allies.

Already old and unhealthy when he came to power, Constantine died on May 22, 1067. His final act was to demand that only his sons succeed him, forcing his wife Eudokia Makrembolitissa to take a vow not to remarry.
Constantine X
Emperor Constantine X of the Byzantine Empire