This research deals with the role of the military forces in the formation of the nation-state in Iran during the Qajar and Pahlavi period. The main question of the research is "What role do the military forces play in the formation of the nation-state in Iran?" For the answer, the historical-analytical method was used and by combining Benedict Anderson's theory of imaginary societies and Huntington's theory about the relationship between the government and military forces; By studying and evaluating the theoretical literature, the role of modernity in the formation of the nation-state is discussed. This process began from the Qajar period and after the defeat of Iran by Russia because of the lack of a regular military force; by sending Iranian students abroad to learn military techniques. They got acquainted with modernity and the way of governance based on it (state-nation) and after returning, they transfer it using the printing industry. This process progressed in the first Pahlavi government with the modernization of the government structure and authoritarianism in its implementation. Among the measures in this direction was the creation of a regular military force (army) and the mandatory law system which was used to create "Another" against Iran (Iranians against non-Iranians) as a factor of socialization and transformed the Iranian identity and led to the incomplete construction of the nation-state in Iran, and this caused the reaction of some social groups in the subsequent developments of Iran.