The Battle of Jalulā was one of the most significant military encounters between the Sasanian Empire and the Muslim Arabs in the early seventh century CE. This battle not only marked a decisive military defeat for the Sasanians but also represented a turning point in the collapse of the symbolic frontier between Ērān and Anērān, a concept that underpinned the ideological and political foundations of the Sasanian state. The central research question is How did the Battle of Jalulā simultaneously of the Ērān/Anērān identity frontier? The main objective of this study is to examine the military, political, and identity dimensions of the battle and to demonstrate its role in the decline of Sasanian ideology. The research hypothesis posits that the Battle of Jalulā marked the end of the Iranšahr`s authority a turning point where military defeat led to ideological collapse and the dissolution of the identity boundaries between Ērān and Anērān. The research method is descriptive-analytical based on historical and library sources. The findings of the study reveal that the weakness of the military structure and the crisis in political leadership led to the Sasanian defeat at Jalulā a defeat that, by collapsing the geographical and symbolic boundaries between Ērān and Anērān, paved the way for the final disintegration of the Sasanian state and the rapid expansion of Islam in Iran.