Leo IV the Khazar

Leo IV the Khazar (; 25 January 750 – 8 September 780) was Byzantine emperor from 775 to 780AD. He was born to Emperor Constantine V and Empress Tzitzak in 750. He was elevated to co-emperor in the next year, in 751, and married to Irene of Athens in 769. When Constantine V died in September 775, while campaigning against the Bulgars, Leo IV became senior emperor. In 778 Leo raided Abbasid Syria, decisively defeating the Abbasid army outside of Germanikeia. Leo died on 8 September 780, of tuberculosis. He was succeeded by his underage son Constantine VI, with Irene serving as regent.

Biography Leo IV was born on 25 January 750AD, to Emperor Constantine V and his first wife, Empress Tzitzak who had been given the Christian name Eirene. Because his mother was a Khazar, Leo was given the epithet 'the Khazar'. Leo was elevated to co-emperor in 751, while still an infant. He became emperor on 14 September 775, after Constantine V died while campaigning against the Bulgarian Empire.

Leo was by this point suffering from tuberculosis, which, combined with the infancy of his son, Constantine VI, gave two of Leo's half-brothers, the caesares Nikephoros and Christopher, hope of attaining the throne. These hopes were crushed when, in 776, Leo elevated Constantine to caesar, declaring him to be his successor. Shortly after this, Nikephoros and Christopher were discovered conspiring against Leo. Despite public opinion supporting the execution of the pair, Leo instead chose to pardon them, although he did exile several other plotters to Cherson.

In 776–777, Khan Telerig of Bulgaria sought refuge in Constantinople, was baptized in the presence of Leo and married a relation of the empress consort Irene of Athens. This demonstrates close relations between the Byzantine Empire and the Bulgars during Leo's reign, which were facilitated by his father Constantine V's successful campaigns against them between 760 and 775, establishing a state of peace.

Leo continued with his father's resettlement policies, relocating prisoners from cities on the Arab border (Germanikeia, Melitene and Theodosioupolis) to newly-constructed military encampments or fortresses (castra) in Thrace.

Campaigns against the Abbasid Caliphate Caliph al-Mahdi of the Abbasids launched an invasion of the Byzantine Empire in 776 with himself present. The Byzantines retaliated in 778, invading Syria with a force made up of the armies of the multiple themes, including: the Opsikion Theme, led by Gregory; the Anatolic Theme, led by Artabasdos; the Armeniac Theme, led by Karisterotzes; the Bucellarian Theme, led by Tatzates; and the Thracesian Theme, led by the favourite commander of the Isaurian dynasty, Michael Lachanodrakon. Lachanodrakon besieged Germanikeia for a time, then lifted the siege (according to Theophanes the Confessor, he was bribed to do so) and began to raid the surrounding countryside, deporting many Jacobite Christians to Thrace. The Abbasids attacked Lachanodrakon while he was raiding, but were decisively defeated by several Byzantine armies. The Byzantine generals who led troops during this battle were given a triumphal entry when they returned to Constantinople. In 779, Leo successfully repelled an attack by the Abbasids against Asia Minor.

Death and succession Leo died of a violent fever, due to his tuberculosis, on 8 September 780. Nine-year-old Constantine became the new emperor with Irene as his regent.