出其不意，攻其不备 (出其不意，攻其不備) chū qí bùyì, gōng qí bùbèi

chū qí bùyì, gōng qí bùbèi phrase to catch an enemy off guard with a surprise attack (idiom, from Sunzi's The Art of War 孫子兵法|孙子兵法)
Domain: Modern Chinese 现代汉语
Notes: (CC-CEDICT '出其不意，攻其不備')