tour of duty

藤崎駐米大使が講演で領土問題をめぐって，日本は冷静に対処すると述べました。また大使は同じ趣旨の論考をHuffington Postに投稿しました。
さて，ここのtour of dutyとは，どういう意味でしょうか。EnDoughくん，どうぞ。（先生代，GP）

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 and Japan 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 in his 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, “Japan is in the midst of a gradual but significant shift to the right.”