Leo was the son of Emperor Constantine V by his first wife, Tzitzak of Khazaria (known as Irene upon her conversion),[REF] the daughter of a Khagan of the Khazars (thought to be Bihar).
Leo's reign coincided with that of the third Abbasid Caliph, Al-Mahdi, who invaded Byzantine lands on successive occasions from 777-780 before ultimately being repulsed by Leo's armies, led by generals such as Michael Lachanodrakon.