The Battle of Jalula (16 AH/637 CE) is 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 Iran and Aniran, a concept that underpinned the ideological and political foundations of the Sasanian state. The central research question is: How did the Battle of Jalula simultaneously lead to the collapse of the Iran/Aniran 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 Jalula marked the end of Iranshahr's authority — a turning point where military defeat led to ideological collapse and the dissolution of the identity boundaries between Iran and Aniran. The research method is descriptive‑analytical based on historical and library sources. The findings reveal that the weakness of the military structure and the crisis in political leadership led to the Sasanian defeat at Jalula — a defeat that, by collapsing the geographical and symbolic boundaries between Iran and Aniran, paved the way for the final disintegration of the Sasanian state and the rapid expansion of Islam in Iran.