Isaac the Armenian was Exarch of Ravenna under the Emperor Heraclius from 625-637, and thereafter Western Roman Emperor in his own right until 651. Hailing from the Kamsakaran clan of Armenia, he gained a reputation for being an able general and administrator during the war with Persia, and was made Exarch in 625 to replace the upstart Eleutherius.
A devout Catholic Christian, Isaac rejected utterly the religious reforms begun by Heraclius after the Third Council of Constantinople. In 637, therefore, with the support of the Pope and the Exarch of Africa, Isaac renounced his loyalty to Constantinople and proclaimed the restoration of the Western Empire, with himself as Emperor. Heraclius, being occupied by two simultaneous wars, was unable to respond, and Isaac used the opportunity to cement his position.
By allying with the Croats of Illyricum, and starting a massive program of shipbuilding at the shipyards of Carthage, he made his empire all but impregnable against an invasion from the east. Then, using his new powers, Isaac raised taxes, recruited more troops, and began a campaign to wipe out the threat from the Lombards. In a series of battles culminating at Ticino, he conquered both parts of the Lombard Kingdom and started the process of assimilating the surviving Lombards to Roman rule.
By 651 the West was at peace and was returning to prosperity. Isaac felt secure enough to negotiate with the new Eastern Emperor, Constans II, who recognised the West's independence in return for Isaac's promise to tolerate Islam.
This peace treaty infuriated the Pope, who encouraged the ambitious and fanatical Exarch of Africa, Gregorius, to rise up and overthrow Isaac. This he did, using the fleet to cut off Isaac's supply and escape routes, eventually entering victorius into Ravenna later that year. Isaac tried to flee in disguise to Illyricum, but was robbed and murdered en route by a gang of thieves.