Byzantine Emperor Basiliscus issues a circular letter (Enkyklikon) to the bishops of his empire, supporting the Monophysite christological position.

The foundation of Constantinople in 330 AD marks the conventional start of the Eastern Roman Empire, which fell to the Ottoman Empire in 1453 AD. Only the emperors who were recognized as legitimate rulers and exercised sovereign authority are included, to the exclusion of junior co-emperors who never attained the status of sole or senior ruler, as well as of the various usurpers or rebels who claimed the imperial title.

Basiliscus was Eastern Roman emperor from 9 January 475 to August 476. He became magister militum per Thracias in 464, under his brother-in-law, Emperor Leo I. Basiliscus commanded the army for an invasion of the Vandal Kingdom in 468, which was defeated at the Battle of Cape Bon. There were accusations at the time that Basiliscus was bribed by Aspar, the magister militum; many historians dismiss this, instead concluding that Basiliscus was either incompetent or foolish for accepting Vandal King Gaiseric's offer of a truce, which the latter used to construct fireships. Basiliscus's defeat cost the Eastern Empire 130,000 pounds (59,000 kg) of gold, causing the empire to hover above bankruptcy for 30 years. When Basiliscus returned to Constantinople, he sought refuge in the Hagia Sophia. His sister, Empress Verina, secured him a pardon and he left the church to retire in Neapolis.

Monophysitism or monophysism is a Christological doctrine that states that there was only one nature—the divine—in the person of Jesus Christ, who was the incarnated Word. It is rejected as heretical by the Catholic Church, Eastern Orthodox Church, Anglicanism, Lutheranism, Reformed Christianity (Calvinist), and all mainstream Protestant denominations, which hold to the dyophysitism of the 451 Council of Chalcedon—as well by Oriental Orthodoxy, which holds to miaphysitism.