By then, the Red Guards were nearly a spent force, and the army had to intervene to save the nation by manning civilian posts. （美国《时代周刊》）

a spent force 翻译为“强弩之末”合适吗？

My comments:

Spent is the past tense and past participle of spend, as in spending money on something.

And if you are a rich person but somehow spend all your money, your money is all spent, meaning all used up.

In that case, you’re no longer wealthy.

Likewise, if you spend all your energy, then all your energy is spent and you’re left exhausted and powerless.

And so, therefore, if you’re a spent force, then you’re not as forceful as before because all of that force you had before is gone.

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本文仅代表作者本人观点，与本网立场无关。欢迎大家讨论学术问题，尊重他人，禁止人身攻击和发布一切违反国家现行法律法规的内容。

About the author:

Zhang Xin（张欣） has been with China Daily since 1988, when he graduated from Beijing Foreign Studies University. Write him at: zhangxin@chinadaily.com.cn, or raise a question for potential use in a future column.