tour of duty
noun [ C ] uk/ˌtʊər əv ˈdjuː.ti/ us/ˌtʊr əv ˈduː.t̬i/ (also tour)
（尤指军人或官员在国外的）服役期，工作期
a period of time that someone, especially a soldier or an official, spends working in a foreign country
The soldiers have just completed a six-month tour in the Philippines. 这些士兵刚刚结束了在菲律宾的半年服役期。