defence forces; defence corps
Refers to a military organization responsible for national defence; often used in proper names like 自衛隊 (Japan Self-Defence Forces) or 国防軍.
That country has a powerful defence force.
The defence forces' exercise will be held next month.
国防軍 is another term for national defence forces, often used in historical or political contexts, whereas 防衛軍 is a broader and more neutral term.
Compound of 防衛 (defence) + 軍 (army, forces). The term is a straightforward Sino-Japanese compound.