The later years of his reign were marked by two major military disasters that had long-term effects: the beginning of the Muslim conquest of Sicily, and the loss of Crete to Andalusian Arab pirates.

Domestically, he supported and strengthened the resumption of official iconoclasm, which had begun again under Leo V. Michael was born c. 770 in Amorium, in Phrygia, into a Cappadocian family of professional peasant-soldiers who received land from the government for their military service.

[2] 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.

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.

[2] 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.

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.

To strengthen his position, he won the support of iconodules by stopping persecution, recalling exiled bishops and offering to reinstate Patriarch Nikephoros I of Constantinople if he ignored the iconoclast controversy, which he refused to do.

Having amassed a large army, perhaps of 80,000 men as some sources report, Thomas marched into Thrace, winning the support of the theme as well as the Armeniacs and Chaldians.

[11][12] The warfare damaged the rural economy, in particular the region around Constantinople, and many Dalmatian coastal towns cast off imperial authority, which was not reinstated until the reign of Basil I (r. 867–886).

Michael tried to reunite the Empire by pardoning many of Thomas' supporters and marrying the daughter of Constantine VI and Maria of Amnia, Euphrosyne, of the illustrious iconoclast Isaurian dynasty, although she herself was an iconodule.

He wrote to the Carolingian Emperor, Louis the Pious (r. 814–840), defending the iconoclast position as represented in the synod of 815, and affirming belief in the veneration of relics.

He gave an account of Thomas the Slav's revolt and appealed to Louis to suppress eastern monks who were spreading anti-Byzantine propaganda in Rome.

Caliph al-Ma'mun mounted a combined land and naval raid in 825, but it did not cause much long-term damage and Michael did not retaliate, leaving the eastern frontier in a hostile stalemate.

[13][18] Michael inherited a seriously weakened military and was unable to prevent the conquest of Crete in 826 by 10,000 Arab pirates from al-Andalus (who had 40 ships), or to recover the island with an expedition.

[19][20][18] Sicily lacked both a dominant political and culture centre, like Ravenna, Rome or Naples, and an autonomous local military elite, so its population were either divided or reacted passively during the crises of the 820s.

Some of Euphemios' supporters deserted him for the imperial government, and he was defeated by another garrison commander, which forced him to flee to the Aghlabid emir, Ziyadat Allah I of Ifriqiya, who recognised his title and gave him a fleet.

Empress Theodora (r. 842–856) defended her husband Theophilos, which mitigated the damnatio memoriae against him and his father Michael, nevertheless the later iconodule sources were highly critical of them.

The civil war, which was the most ferocious since the Heraclian revolt (608–610), gravely weakened the imperial government, which saw the beginning of the century-long struggle over Sicily with the Aghlabids and the loss of Crete to Arab pirates from al-Andalus.