defense of one's country; national defense
Formal or literary term for protecting the nation; often appears in historical, political, or patriotic contexts, and in compound words like 護国神社.
He gave his life for the defense of his country.
Gokoku Shrine enshrines those who fought for the nation.
防衛 is a neutral, everyday word for defense (of a country, team, title, etc.), whereas 護国 is a formal, nationalistic term reserved for defending one's homeland.
保護国 means 'protectorate' (a state under another's protection), while 護国 means 'defending one's own country'; the shared kanji can mislead learners.
Compound of 護 (go, 'protect') and 国 (koku, 'country'). The exact historical derivation is uncertain, but the word has been used in patriotic and religious contexts since at least the Meiji period.