We must build forces that are as impregnable as a rock.

我们必须建立坚如磐石的军事力量。

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A new Iron Curtain is being drawn around Russia. It's not so impregnable or wide as the Soviet one.

一个新铁幕在俄罗斯周围形成，不过这一个并没有苏联时期那么广阔和坚不可摧。

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The failure of the eradication programme created a belief, held by many, that malaria was impregnable to any kind of frontal attack.

消灭规划的失败令人产生一种信念，许多人均抱持这种信念，即任何正面攻击都无法击溃疟疾。

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Just a fortnight ago, the president seemed almost impregnable, with a chance that he might be re-elected unopposed in May.

ECONOMIST: Venezuela

India enjoyed a perfect start to the day, advancing a solid overnight position of 311-5 to a virtually impregnable one of 422-5 soon after lunch.

BBC: Krejza raises Australia's spirits

As the legislation - seen as having been watered down compared to the initial White Paper in 1997 - made its way through parliament, Labour MP Mark Fisher described it as "an amazing defensive edifice for the government...a virtually impregnable fortress".

BBC: Will it end Britain's culture of secrecy?