深沟高垒

Explanation: Deep trenches and high camp. Refers to the strong fortifications. 　　Usage: Joint type; as object, attribute; that strong defense 　　Source: Qin Han Fei, "said Han Fei forest": "General anger, will Shengougaolei; general anger, will slack off." 　　Examples: You are ~, adhere to city. (Yuan Zheng Tingyu "Chuzhao Gong" First off) Thesaurus:  trench bulwark