One of the significant and influential social phenomena during the reign of Reza Shah (Pahlavi I) was militarism—a concept that has often been reductively equated with warfare or military strength. In most existing studies, only partial aspects of this phenomenon have been addressed. The present research takes the nature of militarism during the Pahlavi I period as its central question and, by way of hypothesis, conceptualizes it as “militarism as a social phenomenon.” This refers to a set of externally-oriented, process-driven social policies and practices wherein military reforms are employed as instruments for achieving broader social objectives. To substantiate this claim, the study specifically focuses on one aspect of the social deployment of military transformations—namely, the stage of “narrative construction.” To articulate its hypothesis, the research draws on the concept of “preferred threat constructions.” The findings of this qualitative-interpretive study, conducted through the method of historical sociology, demonstrate that the legitimacy generated through narrative constructions—narratives which portrayed the 1921 coup as the beginning of Iran’s modern history, the expulsion of foreign-controlled troops as a symbol of national independence, internal dissidents and tribal groups as embodiments of corruption and social decay, and the army as the engine of development and the agent of crisis resolution—played a fundamental role in enabling the use of military instruments for the realization of social objectives.