箭无虚发 Every arrow finds its mark
Explanation
形容箭术高明，百发百中。也比喻做事有充分的把握，一定能成功。
Describes superb archery skills; every shot hits the target. It also describes the certainty of successfully accomplishing something.
Origin Story
话说唐朝名将薛仁贵，年轻时曾参加过一次重要的战役。当时，敌军人数众多，气势汹汹，而我军人数少，形势危急。薛仁贵临危不乱，他弯弓搭箭，瞄准敌军，只听得嗖嗖几声，一支支利箭飞射而出，精准无比，敌军应声倒下，无一幸免。薛仁贵的箭法，如同神助一般，百发百中，箭无虚发，大破敌军，最终取得了这场战役的胜利。从此以后，“箭无虚发”便成为后人称赞他神勇箭法的佳话，也成了人们形容办事有把握、一定能够成功的一种说法。
It is said that during the Tang Dynasty, the famous general Xue Rengui participated in an important battle in his youth. At that time, the enemy forces were numerous and aggressive, while our army was outnumbered and the situation was critical. Xue Rengui remained calm under pressure, he drew his bow, aimed at the enemy, only the sound of several arrows flying out and hitting the target could be heard, extremely precise, the enemy troops fell, without a single survivor. Xue Rengui's archery skills, as if divinely aided, every shot hit the mark, defeating the enemy forces and finally winning this battle. Since then, "Jian Wu Xu Fa" has become a story praising his brave archery skills, and also a way to describe something that is certain to succeed.
Usage
用于形容人办事准确有效，有把握，也常用于比喻做事有充分的把握，一定能成功。
Used to describe someone's actions being accurate and effective, with confidence. It's often used to describe having full confidence in accomplishing something.
Examples
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他的箭术非常高明，箭无虚发。
ta de jianshu feichang gaoming, jian wu xu fa.
His archery skills are superb; every arrow finds its mark.
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这次行动必须成功，我们不能让任何一支箭射空，箭无虚发！
zhe ci xingdong bixu chenggong, women buneng rang renhe yizhi jian shekong, jian wu xu fa!
This operation must succeed; we cannot afford to waste a single arrow, every shot must hit its target!