With the increase in defense R&D budget in South Korea, the importance of technological innovation and development has been emphasized. Data pre-investigation, analysis, and provision are also recognized as crucial factors. In this study, big data analysis methods were employed to quantitatively analyze defense-related patents and provide useful information for defense strategies and policy decisions. This research focused on defense patents filed domestically from 2003 to 2022 and attempted an objective analysis. Through frequency analysis of major CPC codes over time, technological trends and changes in key research areas were identified. Association rule mining was conducted to analyze the correlation and convergence levels among technologies. Furthermore, abstract texts of patents were analyzed using TF-IDF analysis to identify keywords in the defense field. It is hoped that the technological trends and convergence levels presented in this study can be effectively utilized in future R&D technology policy formulation.