According to "History of the Byzantine Empire", by A.A. Vasilev, Michael was successful in beating back the incursions of the eastern Arabs and the Russians. During his father's reign and his, however, serious losses were inflicted by the western Arabs. Sicily, Crete, and much of Italy were lost.
He is most remembered however for his debauchery and frivolity. He was nicknamed "The Drunkard". His reign officially began in 842, when he was but three years old. During his minority, his mother, Theodora, was the official ruler of the Empire. She entrusted all government to her favorite, Theoctistus. When Michael came of age, he ordered Theoctistus to be killed and compelled his mother to become a nun.
He took little interest in affairs of state. As a result, his uncle, Bardas, soon came to dominate government affairs. Bardas was treacherously assassinated by Michael's new favorite and adopted son, the future Emperor Basil I. Michael allowed Basil to rule jointly with him for about a year. Basil began to suspect that Michael was plotting against him and had him assassinated in 867 at the age of 28.