Japan Self-Defense Forces; JSDF
Refers specifically to Japan's post-war military organization. Often used in news and formal contexts.
The Self-Defense Forces are also deployed for disaster relief.
He joined the JSDF.
self-defense force
General term for a military force intended for self-defense, applicable to other countries' forces in some contexts, but most commonly understood as Japan's JSDF.
That country has a strong self-defense force.
The government dispatched the Self-Defense Forces to the disaster area.
My older brother joined the Self-Defense Forces after graduating high school.
He worked in the disaster area as a member of the Self-Defense Forces.
自衛隊 refers to Japan's Self-Defense Forces as a whole (land, sea, and air), while 陸上自衛隊 names only the land branch.
米軍 is the United States military, while 自衛隊 is Japan's own Self-Defense Forces, a completely different country's armed forces.
自衛隊 is the umbrella term for all of Japan's Self-Defense Forces, while 航空自衛隊 specifically names the air branch within it.