noun
Military term for a garrison or the act of garrisoning troops, especially in a defensive role. Often used in historical or formal contexts.
その都市には衛戍部隊が駐留していた。
A garrison unit was stationed in that city.
守備隊 is a more common, modern term for a garrison or defense force, while 衛戍 is a formal, somewhat archaic military term.
From Chinese 衛戍／卫戍 (wèishù), meaning 'garrison' or 'defend'. The kanji 衛 means 'defense' and 戍 means 'garrison' or 'guard'.