Occupancy
Noun and する verb
ちゅうとん
あそこには米軍が駐屯しているんだよ。
US armed forces are stationed over there.
Resident soldiers live in barracks when they've been stationed in another country. They have to serve their occupancy for a certain amount of time before they get to go back home.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.