The paper discusses the importance of civil-military cooperation during mass events between 2013 and 2024. We analysed the COVID-19 pandemic, the 2024 Olympic Games in Paris, and the Boston Marathon bombing, highlighting various forms of armed force involvement in supporting civil institutions. We found that the effectiveness of civil-military cooperation depends on a clear division of responsibilities, mutual trust, training, and coordinated procedures. The paper further underscores the need to formalize this cooperation as an inherent component of the national security system.