1, national defense is a knowledge of survival and also a kind of national defense, which refers to the construction and struggle of the army and the political, diplomatic, economic, cultural and other aspects related to the army, defending national sovereignty and territorial integrity and guarding against foreign aggression and subversion.

2. National defense comes into being with the emergence of the country and serves the national interests. Churchill famously said, "We have no eternal friends or enemies, only eternal interests." National defense in this language is directly related to national security, national dignity and social development.

3. Modern national defense, also known as social national defense, national defense and national defense, includes armed construction, national defense system, military science and technology and industry, national defense engineering, military transportation and communication, manpower mobilization, national defense education and national defense laws and regulations. It is a huge and complex system. From the supreme head of state to every citizen, from military to politics, economy, culture, education, science and technology and ideology are closely related to it.

4. Modern national defense takes military forces as the core, including related non-military forces; It attaches importance to the war potential of the country, especially the mobilization efficiency in wartime; It is also a competition of comprehensive national strength based on economy and science and technology. The modern army is an armed group with intensive knowledge and technology, and it emphasizes quality over "sea tactics". The role of national defense in peacetime is deterrence, which requires winning without fighting; The duty of national defense in wartime is actual combat, and the goal is victory.