A country’s social system and national policies can indeed determine the nature of national defense.

The country’s social system and national policies are the basis of the national defense policy. A country's national defense policy is often closely related to its social system, national policies and national security situation. For example, socialist countries usually adopt national defense policies that are consistent with their socialist systems, while capitalist countries usually adopt national defense policies that are consistent with their market economies.

The country’s social system and national policies play an important guiding role in national defense construction. The country's social system and national policies can guide the direction of national defense construction, determine the goals, tasks and priorities of national defense construction, and formulate specific policies and measures for national defense construction. For example, the country's social system and national policies can guide the direction of military construction, determine the goals, tasks and priorities of the military, and formulate specific policies and measures for military construction.

A country’s social system and national policies have an important impact on national defense and security. A country's social system and national policies can affect the national defense and security situation, thereby affecting national defense and security construction. For example, a country's social system and national policies can affect the formulation of military strategies and tactics, thereby affecting national defense and security construction.

The fundamental functions of national defense:

1. Defend national sovereignty: The primary function of national defense is to defend the country’s sovereignty, that is, the country’s supreme power internally and externally, including national territory, sovereignty, Political system, economic system, etc. National defense ensures national security and stability by safeguarding national sovereignty.

2. Maintaining national security: The second important function of national defense is to maintain national security, that is, the country’s political, economic, military, cultural and other security. National defense ensures the stability and security of the country by combating behaviors that threaten national security.

3. Protecting national interests: The third important function of national defense is to protect national interests, that is, the country’s interests in economy, culture, science and technology, etc. National defense ensures the country's economic and cultural development by safeguarding national interests.

4. Promote social harmony: The fourth important function of national defense is to promote social harmony, that is, to promote social harmony and stability by safeguarding national security and maintaining social stability. National defense promotes social development and progress by ensuring social harmony, maintaining social stability.