Michael III 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 an attack by the Rus' on Constantinople. In 863, Petronas defeated and killed the emir of Melitene at the battle of Lalakaon, and celebrated a triumph in the capital.