Zhǐyǒu bǎiliàn-chénggāng de tuánduì cáinéng miànduì zhèyàng de tiǎozhàn.
Only a battle-hardened team can face this kind of challenge.
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history
From 汉·陈琳《武军赋》: a Han-dynasty war rhapsody describing armor of 'steel tempered a hundred times' (百炼精刚). Iron ore was literally folded and hammered again and again by ancient smiths to drive out impurities - the figurative meaning grew directly out of the forge.