The issue of the crime of aggression against Iran in the Twelve-Day War is of great importance from the perspective of international criminal law, especially Article 8 bis of the Rome Statute. This research article examines the crime of aggression within the framework of international criminal law, focusing on the events of the Twelve-Day War between Iran and Israel, and attempts to assess the compatibility of the military actions taken with the elements of the crime of aggression as stipulated in Article 8 bis of the Rome Statute. The subject of the research is important because the crime of aggression, as the most serious act against international peace and security, requires the verification of precise material, psychological, and formal elements, and only includes leaders who had the actual authority to direct or control the act of aggression. The conflict in question, given the organized nature of the attacks and their consequences for the territorial integrity of Iran, provides a suitable space for analyzing existing legal criteria. The main issue of the research is whether the actions taken in this war are consistent with the criteria set out in the Kampala amendments and the definition of aggression in Resolution 3314, and if this compliance is established, what legal and political obstacles prevent the prosecution of the attacking leaders in the International Criminal Court. Examination of the elements of the crime shows that widespread and intentional attacks against the territory of an independent state, in the absence of a valid legal justification.