The story in learner-safe form
城门失火 usually calls up the fuller saying 城门失火，殃及池鱼. The city gate burns, but the pond fish suffer because people draw water or the surrounding damage reaches them. Modern use is valuable because it names harm that spreads beyond the main actors. English speakers should notice the sympathy built into the phrase. The harmed party may not be guilty; they may simply be close to the conflict. The fuller saying matters because the pond fish are the point. A gate catches fire, but fish suffer because the damage spreads through the environment. Modern use often appears when two powerful sides fight and smaller or unrelated parties are harmed. English speakers should preserve that innocence. The phrase is not about direct responsibility; it is about being close enough to the fire to be affected by it. For this entry, the origin note is only the beginning of the explanation. The useful question is why 城门失火 survived as a portable judgment rather than as a decorative allusion. The classical story route gives the reader an image, but the modern sentence must still prove its own fit. A learner should ask three things: what concrete object is being judged, what evidence in the sentence supports that judgment, and what tone the phrase adds that a plain English adjective would not add. This is why the page tests 城门失火 through business collateral harm, workplace conflict, meaning boundary, usage boundary, misuse boundary; each context changes the pressure on the phrase and shows whether the idiom is acting as praise, warning, neutral description, or criticism. The story or usage background also has a translation boundary. 城门失火 can point toward collateral damage, innocent bystanders get hurt, nearby trouble spreads harm, but those English choices are not interchangeable. One version may preserve the image, another may sound natural in a classroom answer, and another may be safer in a workplace or essay sentence. The entry therefore treats public references as source cards, not as a paragraph order to imitate. Headword checks, story labels, and English equivalents are separated first; only after that are they rebuilt into the learner path used here: answer, label, examples, wrong-use clinic, comparison, story, and practice. The most common failure is overextension. Because 城门失火 has a memorable surface, learners may reach for it whenever a topic feels close. The better habit is to compare it with 唇亡齿寒 and 抱薪救火 and with 胸有成竹 before writing. If the rejected phrase is hard to reject, the sentence probably has not supplied enough evidence. If the rejected phrase is easy to reject, the learner can explain the boundary and use 城门失火 with confidence. That is the practical purpose of the origin section: it turns cultural memory into a sentence-level decision instead of leaving the reader with a story and no next action. This retelling is intentionally not a long quotation. It gives the visible action, the mistake or insight, and the modern use boundary so a reader can remember the story without treating every later sentence as a historical claim.