The chronology of the Arab Muslim invasion of Armenia is not clear, Arab and Armenian sources making contradictory statements, with some clarity possible only in regard to the start of the aggression in the 640s, and Theodore Rshtuni's submission in 653. Prior to the Arab invasions, Rshtuni had been appointed the
sparapet (commander-in-chief) of the Armenian forces in the
Armenian Marzpanate and was appointed as the
marzban of Armenia in 634. He defended, alongside the Byzantine general
Procopius, against the first, unsuccessful Arab attack into Armenia in 640. A maneuver that went wrong allowed the Arabs to pillage the capital of
Dvin and take 35,000 inhabitants into slavery. Constans paid special attention to his family's imperiled homeland of Armenia, and he favored Byzantine generals of Armenian extraction to halt Arab advances. Faced with the impending loss of the province, he marched in, spent the winter of 652–3 at Dvin, and returned to
Constantinople the next year after leaving an army in place. The three-year peace with the Arabs broke down in 653, followed by the final Arab conquest of 654. Constans attempted to impose
Chalcedonian doctrines, such as
Monotheletism, on the Armenians, which offended both their clergy and ruling elites. When the Muslims managed to defeat the remaining Byzantine troops in 653, Theodore Rshtuni participated in pushing out the Byzantines and he again recognized Muslim overlordship on very convenient conditions. Theodore's truce with then-governor of Syria and future
caliph,
Muawiyah, left Armenia with a relatively high level of
autonomy, and Arabs concentrated their efforts against the remaining pockets of resistance in the
Sassanid Empire. Another chronology proposes 651 as the year Rshtuni accepted the first truce with the Arabs, and that by 652 he accepted Muawiyah's suzerainty and was appointed
ruler of Armenia. The
Soviet Armenian Encyclopedia of 1978 states that in response to Theodore Rshtuni's treason, Constans personally marshaled his forces and led them to Armenia despite a growing plot against him in
Constantinople by the Armenian commander of the army of
Thrace. Constans secured Armenia and deposed Theodoros, who took refuge on the island of
Akhtamar. Byzantine commander Maurianus was given the task to defend the Armenian frontier. In 654 Maurianus was driven out of Armenia into the
Caucasus and Theodoros was restored. Deciding that Theodoros was untrustworthy, the Arabs sent him to
Damascus, where he died in captivity the following year. Alternative years are 655 for the Muslim campaign during which Theodore Rshtuni was taken to Syria, and 656 for his death. He was replaced as prince by his son-in-law,
Hamazasp IV Mamikonian. His body was brought to his home district of
Rshtunik, where he was buried in the tomb of his forefathers. ==Legacy==