How long have they been at war ?

他们交战有多长时间了？

《牛津词典》

The country is now at war.

这个国家正在打仗。

《牛津词典》

Technically (speaking) , the two countries are still at war.

严格说来，这两国仍在交战。

《牛津词典》

"Let me say this as clearly as I can: The United States is not, and will never be, at war with Islam."

VOA: special.2009.04.11

But secondly again Homer and the poets sing the virtues of men at war.

另外，荷马与其它诗人,歌颂战士的美德；

耶鲁公开课 - 政治哲学导论课程节选

Part of the poem's force derives from the status of this moment as something remembered, and remembered within the context of a nation at war.

诗歌的一部分力量来源于,事情被记起那一刻的状态，并且是在国家处于战争时期的情况下记起的。

耶鲁公开课 - 现代诗歌课程节选

The calamity that sets the pattern for the future occurs while Teddy is at war.

ECONOMIST: New American fiction

The original trial judge, Orlando Hudson, and the new prosecutor, Tracey Cline, are at war.

FORBES: Will Luck Grant Novelist Michael Peterson a New Murder Trial?

No hint of being at war or under siege or standing firm in dark times.

BBC: America's mourner in chief