tour of duty

1. N-COUNT A soldier's tour of duty is a period of time when the soldier is involved in a particular duty or stationed in a particular place such as a war zone. 勤務(wù)

...a Green Beret who served two tours of duty in Vietnam. ...一位兩次在越南執(zhí)行勤務(wù)的綠色貝雷帽成員。