surnamed CHAZA'RUS, emperor of Constantinople (A. D. 775-780).

He belonged to the Isaurian dynasty, and was the eldest son of the emperor Constantine V. Copronymus, whom he succeeded on the 14th of September, 775. He was born on the 25th of January, 750, and received his surname Chazarus on account of his mother Irene, who was a Chazarian princess. Leo, being in weak health, had his infant son Constantine (VI.) crowned in the year after his accession, and his five brothers, Nicephorus Caesar, Christophorus Caesar, Nicetas, Anthemeus, and Eudoxas, took a sacred oath to acknowledge the young Augustus as their future master. This oath, however, they broke repeatedly, formed conspiracies, and were punished with mutilation and exile. After some fruitless attempts at recovering freedom and power, they finally disappeared from the world at Athens, which was their last place of exile. In 777 Teleric, king of the Bulgarians, fled to Constantinople, in consequence of some domestic commotions, and was well received by Leo, although he had behaved very treacherously against Leo's father. In 778 the Arabs invaded the empire. Leo sent against them an army of 100,000 men, commanded by Lachano Draco, who routed them, after they had gained various successes in Syria, in 780: in this battle Othman, the son of the khalif Mahadi or Modi, lost his life. When the news of this victory arrived at Constantinople the emperor was no more among the living: his death took place on the 8th of September, 780. He was succeeded by his infant son Constantine VI., who reigned under the guardianship of his mother Irene. Leo IV. was an honest man, much better than his profligate father, but weak in body and mind.