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
at the death of one 's father or mother - qì xuè jī sǎng
neither spreading about nor branching out-concise - bù màn bù zhī
pressed breast to back and shoulder to shoulder - yā jiān dié bèi