Battle of Avarayr The Battle of Avarayr ( , transliteration in Armenian " Avarayri chakatamart " ) also known as Battle of Vardanants , was fought on May 26 , 451 AD on the Avarayr Plain in Vaspurakan , between the Armenian Army under Vardan Mamikonian and Sassanid Persia . Although the Persians were victorious on the battlefield itself , the battle proved to be a major strategic victory for Armenians , as Avarayr paved way to the Nvarsak Treaty ( 484 AD ) , which affirmed Armenia ' s right to practice Christianity freely . Background . The Kingdom of Armenia was the first nation to officially convert to Christianity , in 301 AD under Tiridates III . In 428 , Armenian nobles petitioned Bahram V to depose Artaxias IV ( Artashir IV ) . As a result , the country became a Sassanid dependency with a Sassanid governor . The Armenians nobles initially welcomed Persian rule , provided they were allowed to practice Christianity ; but Yazdegerd II , concerned that the Armenian Church was hierarchically dependent to the Latin - and Greek - speaking , Orthodox Christian Church , aligned with Rome and Constantinople rather than the Aramaic - speaking , Persian - backed Nestorian Church , tried to compel the Armenian Church to abandon Rome and Byzantium in favor of the Nestorians or simply convert them to Zoroastrianism . He summoned the leading Armenian nobles to Ctesiphon , and pressured them into cutting their ties with the Orthodox Church as he had intended . Yazdegerd II himself was a Zoroastrian rather than a Christian , and his concern was not enforcing a Nestorian orthodoxy but securing political loyalty . According to Armenian tradition , attempts at demolishing churches and building fire - temples were made and a number of Zoroastrian magi were sent , with Persian military backing , to replace Armenian clergy and suppress Christianity . But Yazdegerd ' s policy created , rather than forestalled , a Christian rebellion in Armenia . When news about the compulsion of the nobles reached Armenia , a mass revolt broke out ; on their return , the nobility , led by Vardan Mamikonian , joined the rebels . Yazdegerd II , hearing the news , gathered a massive army to attack Armenia . Vardan Mamikonian sent to Constantinople for aid , as he had good personal relations with Theodosius II , who had made him a general , and he was after all fighting to remain in the Orthodox Church ; but this assistance did not arrive in time . Battle . The 66 , 000 - strong Armenian army took Holy Communion before the battle . The army was a popular uprising , rather than a professional force , but the Armenian nobility who led it and their respective retinues were accomplished soldiers , many of them veterans of the Sassanid dynasty ' s wars with Rome and the nomads of Central Asia . The Armenians were allowed to maintain a core of their national army led by a supreme commander ( sparapet ) who was traditionally of the Mamikonian noble family . The Armenian cavalry was , at the time , practically an elite force greatly appreciated as a tactical ally by both Persia and Byzantium . In this particular case , both officers and men were additionally motivated by a desire to save their religion and their way of life . The Persian army , said to be three times larger , included war elephant s and the famous Savārān , or New Immortal , cavalry . Several Armenian noblemen with weaker Christian sympathies , led by Vasak Siuni , went over to the Persians before the battle , and fought on their side ; in the battle , Vardan won initial successes , but was eventually slain along with eight of his top officers . Outcome . Following the victory , Yazdegerd jailed some Armenian priests and nobles and appointed a new governor for Armenia . The Armenian Church was also unable to send a delegation to the Council of Chalcedon , as it was heavily involved in the war . The Armenian Church would reject the decisions of the Council of Chalcedon , instead adhering to Miaphysitism . Armenian resistance continued in the decades following the battle , led by Vardan ' s successor and nephew , Vahan Mamikonian . In 484 AD , Shah Peroz I signed the Nvarsak Treaty , which guaranteed religious freedom to the Christian Armenians — who were , however , no longer in communion with Rome or Constantinople — and granted a general amnesty with permission to construct new churches . Thus , the Armenians see the Battle of Avarayr as a moral victory ; May 26 is considered to be a holy day by Armenians , and is one of the most important national and religious days in Armenia .