The Arab rule in Armenia lasted for almost two and half centuries (640-886). The Arab domination, however, was heavy handed, and time after time, the Armenian nobility rebelled against oppression and excessive taxes. As it had happened under Persian rule, several of those rebellions were headed by the Mamikonian princes.
Mushegh Mamikonian was elected Prince of Armenia in 748 after Ashot Bagratuni was blinded by the Arabs. He was the brother of Grigor Mamikonian, who led the rebellion of 748-750 against the Arabs. It seems that he was not confirmed by the caliphate and in 753 he was replaced by Sahak Bagratuni. Sahak’s brother, Smbat Bagratuni, became sparapet (generalissimus) in the same year and succeeded his brother around 770, when the latter was murdered by the Arabs.
In 774 Artavazd Mamikonian killed the Arab tax collector in Gumayri (nowadays Gumri) and started a new rebellion. However, he and his allied princes were defeated by the Arab general Muhammad in Georgia and had to leave towards Mingrelia, where they obtained lands from the Byzantine emperor.
Meanwhile, the rebellion continued in Armenia, now led by a coalition of nobles headed by Mushegh Mamikonian. The latter killed several Arab tax collectors and found refuge in the impregnable fortress of Artagers, undertaking various punitive expeditions in the area of Karin (Erzerum). His victories encouraged many nobles and even sparapet Smbat Bagratuni to join him. The Armenian laid siege to Karin with 5,000 soldiers.
However, an Arab army of 30,000 soldiers, headed by Amr ibn Ismayil, invaded Armenia, and after the battle of Arjesh, near Van, they entered the province of Bagrevand and camped near the village of Artzni, on the Aratzani River (eastern branch of the Euphrates). The Armenian army, mostly composed by villagers and led by Mushegh Mamikonian, was forced to lift the siege of Karin and confront the Arabs at Artzni. The battle started at sunrise. At the beginning, the Armenians made the Arabs flee, but the latter received reinforcements and started a counteroffensive. In the end, the superior Arab forces defeated the Armenian heroic defense. Their leader Mushegh Mamikonian, Smbat Bagratuni, and other noblemen perished in the battle and the rebellion practically came to an end.
After this rebellion, it is generally accepted that the Mamikonian family lost much of its military power and the Bagratunis started their rise, which would end a century later, in 886, with their ascension to the throne of Armenia.