兵临城下

Explanation: The enemy has come to their own walls below. Analogy the situation very critical. 　　Usage: The main predicate; as predicate, object, clause; described the critical situation is very dangerous 　　Source: Yuan Anonymous "Maling Road": "One day a hope, around the corner edge of Ho." 　　Examples: If Hou ~, approaching trench side, and then repelling the enemy, things have been delayed carry on. (Ming Luo, "Three Kingdoms" thirty-back) Thesaurus:  Enemy state foreign aggression, Large contingent Yajing