(Ῥωμανὸς ὁ Διογένης), Byzantine emperor from A. D. 1067-1071, was the son of one Constantine Diogenes, a by the rather extravagantt character, who conspired against the emperor Romanus Argyrus, but escaped pursuit by leaping out of a high window. Romallnus Diogenes was the grand-nephew of Romanus Argyrus, through his mother; and enjoying the patronage of the court notwithstanding his either's conduct, soon rose to the dignities of patrician and duke of Sardica or Triaditza. In the reign of Constantine X. Ducas, he solicited the place of Magnus Vestiarius, and having received the answer: "Deserve it through your merite," forth with returned to sardica, sallied out with the garrison, and routed a party of Patzinegue marauders, of whose heads he sent a collection to Constantinople. The emperor returned the compliment by granting him desired appointment, adding: "You owe your preferment not to me, but to your sword." This piqued Romanus; and from that time he entertained schemes of rebellion and of raising himself to the throne. After the death of Conistantine, and duiring the reign of his widow Eudoxia, he became bolder; but his manoeuvres were seen through, and he was arrested, tried, and sentenced to death. Previous to execution he was presented to the empress; and as he had obtained great military renown, and was besides a remarkably handsome man, he made such a visible impression upon Endoxia, that his judges thought it convenient to annul their sentence, in consequence of which he was sent into nominal exile in his native country Cappadocia. Two days after his departure he was ioined by some messengers of the empress, who ordered him to return to Constantinople. At his arrival there he was immediately appointed commander-in-chief of the army. The end of this farce was his marriage with the empress, and his proclamation as emperor three days after their marriage. Constantine X., however, had left three sons, who considered themselves prejudiced through the accession of Romrnanus, and entered into a dantgerouse gerous plot against his life; but their mother scceeded in pacifying them, and submitting them to her authority. There remained, however, a strong party of malcontents at the court, composed of eminent stand hihii-born men. Romans, active and energetic, not only counteracted their plans, but introduced measures of radical reform into the corrupted administration, and freed himself from the authority of his wife, by leaving Constantinople aud keeping his court on the Asiatic side of the Bosporus.
To these domestic quarrels the Turks put a sudconsequence den end. Their sultan, Alp-Arslàn, approached by rapid marches from the shores of the Caspian and the highlands of northern Persia, while one of his lieutenants attacked Syria. Romanus took the field against them with his usual energy and promptitude. His intention was to cover Syria, and he was already on its frontiers when he was informed of the progress of the Turkish arms in the North. He consequently left Syria to his generals, and marched to Pontus with such rapidity, that he surprised and routed several Turkish bodies stationed on its fiontier. This was sufficient to keep the main body of the Turks within Persia. Ro. manus therefore hastened hack to Syria. He made a successful campaign down to Antioch and up again along the Euphrates. and wherever he carried his arms the enemy was worsted. One of his generals, less fortunate, or less skilful, was surprised The Turks, and lost the day and half of his army. Romanus flew to his support; and in a nocturnal engagement, took the camp of the Turks and routed them with great slaughter (20th of November, 1068). He then marched again up the Euphrates as far as Ara, constantly annoyed by the light troops of the enemy; but he placed his troops in good and safe winter-quarters, and returned to the capital. Eudoxia, reconciled to her husband, had meanwhile governed the state with wisdom; and, in acknowledgment of the vicitories of the emperor, presented him with a sort of miscellaneous work, entitled "Ionia," which she had just finished. The campaign was renewed in 1069, and the imperial arms were again successful, though not uniformly so, as the Turks succeeded in taking and pillaging Iconium. The third campaingn in 1070, was carried on under the commandin-chief of Manuel Comnenus, the emperor requir ing repose after so many fatigues. Ere long, news