Although he briefly lost control over the Albanian lowlands and its capital, Partaw, his guerrilla warfare forced the Sasanians to grant him more autonomy.

He took the safe route by acknowledging the suzerainty of the Rashidun Caliphate, but also instructed Juansher to establish contact with the Byzantine emperor Constans II (r. 641–668) and offer his services.

Juansher submitted to the Byzantines, but this was implemented in practice only during the civil war in the caliphate between 656–661, when Constans II managed to exert his influence over all of the Southern Caucasus.

He was succeeded by his nephew Varaz-Tiridates I. Albeit a Christian, Juansher still participated in activities related to Zoroastrianism, the official religion of the Sasanian Empire.

[16] When the Arabs later resumed their attacks and besieged Ctesiphon, Juansher led a force 3,000 soldiers on the right side of the Tigris River, being assigned to protect Yazdegerd III so he could move out of the city.

In 644/45, Juansher went back to Albania through Adurbadagan (in present-day northwestern Iran),[18] most likely due to losing faith in the Sasanian Empire, realizing its impending downfall.

[19][20] Although the Albanian lowlands and its capital, Partaw, were swiftly taken back by Sasanian forces, Juansher's guerrilla warfare proved to be extraordinarily effective, especially after he won the support of prominent figures in the neighbouring Principality of Iberia.

The quick military response Juansher gave to a later Sasanian attempt to regain control over Albania demonstrated that the balance of power was still shifting in his favour.

During this period (most likely during the end of the 640s), as other spahbeds gained more control over their own territories, the Sasanian Empire was fragmenting into a network of regional rulerships that would not necessarily form a united front against the Muslim invaders.

He took the safe route by acknowledging the suzerainty of the caliph, but also instructed Juansher to establish contact with the Byzantine emperor and offer his services.

When Juansher visited to see Constans II in person twice during his Southern Caucasian advance in 660–661, he received clear signs of favor on both occasions.

He was officially anointed as king of "all the eastern peoples" at his second audience in the spring of 661, making him a client ruler comparable to Hamazasp IV Mamikonian in Armenia.

[25] Juansher reportedly played an important role in the decision (Constans II was assassinated on 15 July 669), being in return rewarded with many gifts, and with Siwnik added to his domain.

"[27] He also adds that "Perhaps Juanšer had baulked at the thought of sharing responsibility for killing the senior Christian ruler appointed by God to manage earthly affairs.

[29][30] Despite being a Christian, Juansher continued to take part in the traditional Zoroastrian New Year's Feast of Nawasard with his personal bodyguards, and delight in the pagan performances of the gusank ("ministrels").