An unexpected accident
The idiom ch ū D í y ì w à I is used to explain the unexpected action of the enemy.
The source of Mao Zedong's "operational policy on the Pingjin campaign": "this kind of plan is unexpected to the enemy, and it is difficult for the enemy to detect it before you finally complete the deployment."
An unexpected accident
talk of everything under the sun - tán tiān shuō dì
harass the people and waste money - láo mín fèi cái