北面称臣

Explanation: South to north side of Ancient monarchs, courtiers Meet the monarch is facing north, referring to surrender to others. 　　Usage: Partial official; as predicate, object; containing derogatory 　　Source: Qian Han, "Historical Records of Health Lu Jia Biography": "king should Jiaoying, north to concede defeat." Thesaurus:  bow one's head Declare oneself a vassal