里应外合

Pronunciation: lǐ yìng wài hé Literal meaning: Inside support outside cooperation

Origin & Usage

The idiom 里应外合 (lǐ yìng wài hé) is commonly used in classical Chinese to describe a strategic collaboration where internal and external forces work together to achieve a common goal. The phrase is composed of four characters: 里 (lǐ, inside), 应 (yìng, respond), 外 (wài, outside), and 合 (hé, cooperate). This idiom is often associated with military tactics, where an internal faction coordinates with an external force to launch a successful attack. Its earliest known usage is in the Yuan dynasty play '豫让吞炭' by Yang Zi, which describes a scenario where internal and external forces collaborate to flood an enemy army. In modern contexts, 里应外合 is used to describe any situation where internal and external parties collaborate effectively, such as in business or political strategies.

Examples

English: "The plan was successful because the team coordinated perfectly with external partners."

Chinese: 这个计划之所以成功，是因为团队里应外合。