navy; naval force
Refers to a nation's military sea force. Often used in historical contexts (e.g., 日本海軍) or modern naval forces.
彼は海軍に入隊した。
He enlisted in the navy.
日本海軍の歴史について学ぶ。
I study the history of the Imperial Japanese Navy.
My older brother joined the navy after graduating high school.
He currently belongs to the navy.
That general commanded the navy.
army and navy
(Imperial) Japanese Navy