A Tang dynasty magistrate named Wang Lu was corrupt. When one of his clerks was accused of corruption, Wang Lu read the charges and trembled — because they described his own crimes. He wrote on the document: "Though you beat the grass, I — the snake — am already startled."
The phrase "打草惊蛇" (beating the grass to startle the snake) became the Chinese idiom for alerting an enemy through careless action — doing something that reveals your intentions to those you hoped to catch off guard.
汝虽打草，吾已惊蛇。
汝虽打草，吾已惊蛇。
Reflection & Analysis · 寓意解读
Core Wisdom
The careless investigation that alerts the corrupt is worse than no investigation at all. Strike only when you are ready — and only when the snake does not know you are there.
Wang Lu's confession is involuntary and darkly comic. He was not the target of the investigation — but the investigation reminded him of his own guilt. The idiom's military application is more straightforward: do not reveal your position before you are ready to attack.