Warfare and foreign policy
The internal stabilisation of the state was not entirely matched along the frontiers. Although the Abbasid Caliphate was no longer launching major invasions, and raids were led by local amirs along the frontier rather than the Caliph himself, Byzantine forces were defeated by the Abbasids in Pamphylia, Crete, and on the border with Syria, but a Byzantine fleet of 85 ships did score a victory over the Arabs in 853. There were also many operations around the Aegean and off the Syrian coast by at least three more fleets, numbering 300 ships total. The Byzantines were able to successfully assault Damietta in Egypt in 853. In the 820s, Andalusian Arab pirates seized Crete, which Theoktistos attempted to regain in the first year of the regency, though unsuccessfully. Bardas was planning to sail there but was murdered on the instigation of Basil in 866. The recapture was not achieved until 961, long after Michael's reign.
A conflict between the Byzantines and the First Bulgarian Empire occurred during 855 and 856. The Byzantine Empire wanted to regain its control over some areas of Thrace, including Philippopolis and the ports around the Gulf of Burgas on the Black Sea. Byzantine forces, led by the emperor and the caesar Bardas, were successful in reconquering a number of cities – Philippopolis, Develtus, Anchialus and Mesembria among them – as well as the region of Zagora. At the time of this campaign the Bulgarians were distracted by a war with the Franks under Louis the German and the Croatians. In 853, Khan Boris I of Bulgaria had allied himself to Duke Rastislav of Moravia against the Franks. The Bulgarians were heavily defeated by the Franks; following this, the Moravians changed sides and the Bulgarians then faced threats from Moravia.
Following an expedition led by Michael's uncle and general, Petronas, against the Paulicians from the eastern frontier and the Arab borderlands in 856, the imperial government resettled them in Thrace, thus cutting them off from their coreligionists and populating another border region. The Paulicians, whose power centre was Tephrike, were heavily persecuted after the restoration of icons as they were deemed unorthodox. It was only in 872 that Christopher, Domestic of the Schools, defeated their leader Chrysocheir, and Tephrike was taken in 878. Michael was also responsible, as per the writings of Constantine VII, for the subjugation of the Slavs settled in the Peloponnese.
Michael took an active part in the wars against the Abbasids and their vassals on the eastern frontier from 856 to 863, and particularly in 857 when he sent an army of 50,000 men against Emir Umar al-Aqta of Melitene. In 859, he personally led a siege on Samosata, but in 860 had to abandon the expedition to repel a naval attack by the Rus' on Constantinople. The Rus' fleet plundered the outer suburbs of the city but left of their own volition, probably because they had acquired sufficient booty. The subsequent relationship with the Rus' was mixed; they requested a Byzantine mission which was short-lived, and engaged in further raids but also trade in the tenth century. It was only in the late tenth century that the Christianisation of the Rus' was achieved by Grand Prince Vladimir of Kiev.
Soon after the raid, Duke Rastislav requested a Byzantine mission, perhaps to secure a political counterweight to his neighbours; the Franks and the Bulgars. In 863, they sent Cyril and Methodius, who were from Thessalonika. They developed the first Slavic alphabet, the Glagolitic alphabet, and translated many religious texts into this new literary language. Their mission ceased when Rastislav died and other Slavic princes as well as the Franks pressured them. Nevertheless Cyril, Methodius and their disciples were influential in the newly Christian Bulgaria, where they were exiled to from Moravia in 885. They were installed at Ohrid and Pliska, where they were charged with the creation of a Slavic clergy and the expounding of Christianity in the Slavic vernacular, although Greek remained the liturgical and ceremonial language.
In 863, Petronas defeated and killed the emir of Melitene at the Battle of Lalakaon, and celebrated a triumph in the capital. The year 863 is seen as a turning point in the Arab-Byzantine wars, after which the Byzantines began to go on the offensive, leading to their triumph in the tenth century.
Within the decentralising Abbasid Caliphate, the Armenians, who were vassals of the Abbasids, even participating in the Sack of Amorion of 838, gained a degree of independence. Ashot I of Armenia was crowned king of Armenia in 884, and recognised by Michael and Basil as "prince of princes". Friendly relations between Byzantium and Armenia continued into the tenth century, to the benefit of Byzantine eastward expansion.
