tour of duty(回答)

大変遅くなりましたが先輩からのご指名質問にお答え致します。質問内容はここでのtour of dutyについてです。tour of duty - 田邉祐司ゼミ 常時英心：言葉の森から
Ambassador Fujisaki Disputes War Talk
By Peter Landers

A few weeks ago, the Economist put a picture of the Senkaku/Diaoyu islands on its cover and asked, “Could China andJapan really go to war over these?” A turtle depicted swimming by answers, “Sadly, yes.”

Japan’s ambassador to the U.S., Ichiro Fujisaki, held up a copy of the magazine in a speech in Washington Thursday and shelled the turtle’s analysis. “That’s not going to happen,” he said. There was no need, he said, for the parties to get inflamed.

“We are not going to raise tensions and try to bring it up emotionally,” said Mr. Fujisaki, who has served as Tokyo’s envoy to Washington for the last four years and has a month remaining inhis tour of duty. Still, he implicitly blamed China and South Korea for the recent tensions over small islands, saying, “This is not started by us, by Japan.”

The ambassador outlined similar views in a piece for Huffington Post this week, in which he also tackled what he called “arguments in the U.S. media that nationalism is growing in Japan.” Mr. Fujisaki may have been thinking, among other pieces, of a front-page article in the Washington Post on Sept. 20 that began, “Japanis in the midst of a gradual but significant shift to the right.”

tourと聞くと「旅行、見学」などの意味が最初に想起されますが、ここではその意味ではありません。tourには「(特に軍隊・外交官の)外国勤務時間」という意味(『ジーニアス英和辞典』第4版、大修館書店)があります。finish one's tour of dutyで「海外勤務を終える」となりますね。ここでは「海外赴任の期間」といった意味でしょうか。
tourもdutyも高校までに習う単語ですが、こんな表現がある事は初めて知りました。GP先輩、ありがとうございました。(EnDough by mob)