Prior to the Arab invasions, Rshtuni had been appointed the sparapet 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. He was unable to prevent the Arabs from pillaging the capital of Dvin in 642. He gained a victory over the Arabs, for which he was recognized as ruler of Armenia by Constans II in 643. Constans paid special attention to his family's imperiled homeland of Armenia, and he favored Byzantine generals of Armenian extraction to halt Arab advances. Meanwhile, the strength of Arab assaults continued to increase. Theodore eventually concluded a truce with then governor of Syria, Muawiyah I in 651, and Arabs concentrated their efforts against the remaining pockets of resistance in the Sassanid Empire. Finally, by 652 Rshtuni, despairing of further resistance, accepted Muawiyah's suzerainty and was appointed ruler of Armenia. Rshtuni was able to negotiate a treaty that left Armenia with a relatively high level of autonomy. In response, Constans personally marshaled his forces and led them to Armenia despite a growing plot against him in Constantinople, ironically by the Armenian commander of the Army of Thrace. Constans secured Armenia and deposed Theodoros, who took refuge on the island of Akhtamar. A Byzantine commander named 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. He was replaced as prince by his son-in-law, Hamazasp Mamikonian. His body was brought to his home district of Rshtunik, where he was buried in the tomb of his forefathers.
Legacy
According to Manuk Abeghian and a number of other scholars, the popularity of Rshtuni in Armenia manifested itself in the character of K'eṛi T'oros in the epic poem of David of Sasun. The Armenian writerTserents also wrote a historical novel called Theodoros Rshtuni.
