National defense refers to the strategies and actions taken by a country to protect its sovereignty, territory, and citizens from external threats. This includes maintaining armed forces, such as the Army, Navy, and Air Force, which are responsible for responding to military threats and ensuring security. National defense also involves intelligence gathering and cooperation with other nations to prevent conflicts. In addition to military readiness, national defense encompasses cybersecurity measures to protect against digital threats and espionage. Governments often allocate significant resources to research and development of advanced technologies, such as drones and missile defense systems, to enhance their defensive capabilities and deter potential aggressors.