In the era of global dynamics and the complexity of security challenges, this research explores a new conceptual framework by examining the mediating role of Gross Regional Domestic Product (GRDP) in the combined influence of the Human Development Index (HDI) and Dependency Ratio (DR) on the Defense Budget of a region. Starting from a general understanding of economic growth, human wellbeing, and demographic pressures, this study focuses on the interactive relationships among these key variables and how GRDP can manage the complexity of these dynamics. The study employs regression analysis and mediation techniques with IBM SPSS 25 to enhance previous research by introducing GRDP as a mediator, using secondary data from sources like the Central Statistics Agency. The data population spans 10 years, from 2013 to 2022. Employing purposive sampling, 29 samples were obtained, resulting in 290 units of analysis. The results indicate a significant positive influence of the Human Development Index on Gross Regional Domestic Product, a significant negative influence of Dependency Ratio on Gross Regional Domestic Product, a significant positive influence of the Human Development Index on the Defense Budget, no significant influence of Dependency Ratio on the Defense Budget, a significant positive influence of Gross Regional Domestic Product on the Defense Budget, a positive influence of the Human Development Index on the Defense Budget mediated by GRDP, and no influence of Dependency Ratio on the Defense Budget mediated by GRDP. The study suggests that future research explore alternative proxies for the variables included in this study.