Founder of the Amorian Dynasty

Michael was born in Amorium, in Phrygia, into a Cappadocian family of professional peasant-soldiers who received land from the government for their military service. They may have been members of the sect of the Athinganoi. Michael first rose to prominence as a close aide (spatharios) of the general Bardanes Tourkos, alongside his future antagonists Leo the Armenian and Thomas the Slav. He married Bardanes' daughter Thekla, while Leo married another daughter. Michael and Leo abandoned Bardanes shortly after he rebelled against Emperor Nikephoros I in 803, and they were rewarded with higher military commands: Michael was named the Emperor's Count of the Tent. Michael was instrumental in Leo's overthrow of Michael I Rhangabe in 813, after Rangabe's repeated military defeats against the Bulgarians. Under Leo V, Michael was appointed to command the elite tagma of the Excubitors.

Thekla and Michael had only one known son, Theophilos (813 - 20 January 842). The existence of a daughter called Helena is possible but there is a contradiction between different sources. Helena is known as the wife of Theophobos, a patrician executed in 842 for conspiring to gain the throne for himself. George Hamartolos and Theophanes report him marrying the sister of the Empress Theodora. Joseph Genesius records Theophobos marrying the sister of the Emperor Theophilos. Whether Helena was sister or sister-in-law to Theophilos is thus unclear.

Michael became disgruntled with Leo V when he divorced Michael's sister-in-law. In late 820, agents of the Postal Logothete uncovered a plot led by Michael to overthrow Leo, who then imprisoned Michael and sentenced him to death by burning. Empress consort Theodosia secured a postponement of the execution until after Christmas. This allowed Michael to rally undetected plotters to assassinate Leo on Christmas morning in the palace chapel and castrate his sons to prevent the continuation of his dynasty. Michael was immediately proclaimed emperor, while still wearing prison chains on his legs. Later the same day, he was crowned by Patriarch Theodotus I of Constantinople.

In his internal policy, Michael II supported iconoclasm, but he tacitly encouraged reconciliation with the iconodules, whom he generally stopped persecuting, allowing those exiled by Emperor Leo V the Armenian to return. These included the former patriarch Nikephoros, Anthony the Confessor, and Theodore the Stoudite, who failed, however, to persuade the emperor to abandon iconoclasm. Michael also did not restore the exiled iconodules to their previous positions. Theodore also requested permission to restore icons, resume relations with the bishop of Rome and recognise him as the head of all churches and therefore arbiter of disputes. Michael allowed iconodules to follow their conscience outside of Constantinople but did not make any further concessions, refusing to change imperial policy and banning discussion of the Council of Hieria (754), Second Council of Nicaea (787) and Council of Constantinople (815). When Patriarch Theodotos died in 821, Michael appointed the iconoclast Antony, bishop of Syllaion, against the aspirations of the iconodules.

Michael maintained his policy of compromise and neutrality between iconoclasm and iconodulia until his death, and was supported throughout by Patriarch Antony. In October 829, Michael ordered the release of prisoners, reflecting his moderate policy. On 2 October, he died from kidney failure. He was succeeded peacefully by his son Theophilos and Theophilos's stepmother Euphrosyne, since Theophilos was only seventeen years old.