national defense forces; national security forces
Refers to a country's military forces responsible for national defense. Often used in political or historical contexts, such as discussions about Japan's Self-Defense Forces or other nations' militaries.
The role of the national defense forces is to protect the country.
That country has a powerful national defense force.
軍隊 is a broader term for 'military' or 'armed forces', not necessarily limited to defense.
Compound of 国防 (national defense) and 軍 (army, forces). The term is a straightforward Sino-Japanese compound.