The Persians were not as successful as the Byzantines in their efforts to assimilate the strongly individualistic Armenian people. The misguided attempt of the Persian Sasanian king Yazdegerd II to impose the Zoroastrian religion upon his Armenian subjects led to war in 451. The Armenian commander St. Vardan Mamikonian and his companions were slain at the Battle of Avarayr (June 2?, 451), but the Persians renounced their plans to convert Armenia by force and deposed their marzpān Vasak of Siuniq, the archtraitor of Armenian tradition.

The revolt of 481–484, led by Vahan Mamikonian, Vardan’s nephew, secured religious and political freedom for Armenia in return for military aid to Persia, and with the appointment of Vahan as marzpān the Armenians were again largely the arbiters of their own affairs. Their independence was further asserted in 554, when the second Council of Dvin rejected the dyophysite formula of the Council of Chalcedon (451), a decisive step that cut them off from the West as surely as they were already ideologically severed from the East. (According to the dyophysite formula, Christ, the Son of God, consists of two natures, “without confusion, without change, without separation, without division.”)

In 536 the Byzantine emperor Justinian I reorganized Byzantine Armenia into four provinces, and, by suppressing the power of the Armenian nobles and by transferring population, he completed the work of Hellenizing the country. In 591 its territory was extended eastward by the emperor Maurice as the price of helping the Sasanian king Khosrow II regain the Persian throne. After transporting many Armenians to Thrace, Maurice (according to the Armenian historian Sebeos) advised the Persian king to follow his example and to send “this perverse and unruly nation, which stirs up trouble between us,” to fight on his eastern front. During the war between the emperor Phocas and Khosrow, the Persians occupied Byzantine Armenia and appointed a series of marzpāns, only to be ousted by the emperor Heraclius in 623. In 628, after the fall of Khosrow, the Persians appointed an Armenian noble, Varaztirotz Bagratuni, as governor. He quickly brought Armenia under Byzantine rule but was exiled for plotting against Heraclius (635).

The Mamikonians and Bagratids

The first, unsuccessful, Arab raid into Armenia in 640 found the defense of the country in the hands of the Byzantine general Procopius and the nakharar Theodor Rshtuni. Unable to prevent the pillage of Dvin in 642, Theodor in 643 gained a victory over another Arab army and was named commander in chief of the Armenian army by the Byzantine emperor Constans II Pogonatus. In 653, after the truce with Muʿāwiyah, then Arab governor of Syria, Constans voluntarily surrendered Armenia to the Arabs, who granted it virtual autonomy and appointed Theodor as governor (ostikan).

Theodor’s successor, Hamazasp Mamikonian, sided with Byzantium, but after 661 Arab suzerainty was reestablished, although Byzantine-Arab rivalry, Armenian resistance, and reluctance to pay the tribute made the region difficult to govern. An unsuccessful revolt led by Mushegh Mamikonian (771–772) resulted in the virtual extinction of the Mamikonians as a political force in Armenia and in the emergence of the Bagratunis and Artsrunis as the leading noble families. (See Bagratid dynasty.) The Arabs’ choice in 806 of Ashot Bagratuni the Carnivorous to be prince of Armenia marked the establishment of his family as the chief power in the land. The governor Smbat Ablabas Bagratuni remained loyal to the caliph al-Mutawakkil when al-Mutawakkil sent his general Bughā al-Kabīr to bring the rebellious nakharars to submission, although Smbat too was dispatched in 855 with the rest of the captive nobles to Sāmarrāʿ.

The election by the nobles of Smbat’s son Ashot I (the Great), who had been accepted as “prince of princes” by the Arabs in 862, to be king of Armenia in 885 was recognized by both caliph and emperor. Throughout the 10th century, art and literature flourished. Ashot III (the Merciful; 952–977) transferred his capital to Ani and began to make it into one of the architectural gems of the Middle Ages.

The Bagratids of Ani—who bore the title shāhanshāh (“king of kings”), first conferred upon Ashot II (the Iron) by the caliph in 922—were not the sole rulers of Armenia. In 908 the Artsruni principate of Vaspurakan became a kingdom recognized by the caliph; in 961 Mushegh, the brother of Ashot III, founded the Bagratid kingdom of Kars; and in 970 the prince of Eastern Siuniq declared himself a king.

By the time of the invasions of the Turkic Seljuqs in the 11th century, the Armenian kingdoms had already been destroyed from the west. The province of Taron had been annexed to the Byzantine Empire in 968, and the expansionist policy of the Byzantine emperor Basil II finally extinguished Armenian independence. The possessions of David of Tayq were annexed in 1000 and the kingdom of Vaspurakan in 1022. In the latter year, the Bagratid king of Ani, Yovhannes-Smbat, was compelled to make the emperor heir to his estates, and in 1045, despite the resistance of Gagik II, Ani was seized by Constantine IX Monomachus.

The Byzantine conquest was short-lived: in 1048 Toghrïl Beg led the first Seljuq raid into Armenia, in 1064 Ani and Kars fell to Toghrïl’s nephew and heir Alp-Arslan, and after the Battle of Manzikert (1071) most of the country was in the hands of the Seljuqs. In 1072 the Kurdish Shāddādids received Ani as a fief. A few native Armenian rulers survived for a time in the Kiurikian kingdom of Lori, the Siuniqian kingdom of Baghq or Kapan, and the principates of Khachen (Artzakh) and Sasun. In the 12th century many former Armenian regions became parts of Georgia, and between 1236 and 1242 the whole of Armenia and Georgia fell into the hands of the Mongols. Armenian life and learning, centred around the church, continued in monasteries and village communities.