maintain an army

Maintain an army for a thousand days to use it for an hour.

养兵千日,用兵一时.

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To give you an idea of the size of the Earth, I will tell you that before the invention of electricity it was necessary to maintain, over the whole of the six continents, a veritable army of 462511 lamplighters for the street lamps.

为了使你们对地球的大小有一个概念，我想要告诉你们：在发明电之前，在六个大洲上，为了点路灯，需要维持一支为数四十六万二千五百一十一人的真正大军。

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