Constantine Diogenes

Constantine Diogenes was a prominent Byzantine Greek general of the early 11th century, active in the Balkans.

Biography
Constantine Diogenes is the first notable member of the noble Cappadocian Diogenes family, which played an important role in 11th-century Byzantium. Constantine began his career as a commander of one of the western tagmata during the reign of Basil II (r. 976–1025), in the latter's campaigns against Bulgaria. In 1014, he participated in the decisive Byzantine victory at the Battle of Kleidion, and he subsequently succeeded Theophylact Botaneiates as commander of Thessalonica with the rank of patrikios, making him the second senior-most general of the Empire in the Balkans after David Arianites. In 1018, he was charged with mopping up the last remaining centers of Bulgarian resistance. He took Sirmium and was named its commander (archon), with his authority extending over the vassal Serbian statelets of Raška. His title was possibly that of "strategos of Serbia" (Greek: στρατηγός Σερβίας), which is attested in a seal attributed to him. Diogenes was ordered by Basil II to subdue Sermon of Srem, a vassal to Bulgarian Tsar Samuil, in order to consolidate Byzantine control of the northern Balkans. Consequently, Diogenes invited Sermon to a meeting at the estuary of the river Sava in the Danube, but it was a trap: Sermon was seized and killed.

Around 1022 or 1025, Constantine succeeded Arianites as overall Byzantine commander (strategos autokrator) of conquered Bulgaria. In this capacity, he repelled a large Pecheneg invasion in 1027. In the same year, he was withdrawn south to Thessalonica, but retained, at least nominally, his role as overall commander, as attested by another seal naming him "anthypatos, patrikios and doux of Thessalonica, Bulgaria and Serbia".

Constantine had been married to an anonymous daughter of Basil Argyros, brother of Emperor Romanos III Argyros (r. 1028–1034), but in 1029 he was accused, along with other prominent Balkan generals such as Eustathios Daphnomeles, of conspiring against the emperor with the porphyrogenita Theodora. He was transferred east as strategos of the Thracesian theme, but soon after recalled to Constantinople where he was imprisoned and later blinded. Theodora herself was tonsured and placed in a convent, but she apparently continued to conspire with Diogenes, who planned to take advantage of Romanos's absence on campaign in the East (in 1032) to escape to the Balkans. The plot was leaked to Romanos by Theophanes, metropolitan of Thessalonica, and the conspirators were arrested. Diogenes was brought to the Palace of Blachernae for interrogation by John the Eunuch, but he committed suicide rather than confess under torture and implicate his fellow conspirators.

Constantine's son Romanos Diogenes became a successful general and would eventually rise to become Byzantine emperor in 1068–1071.