chū qí bù yì
to do sth when least expected (idiom); to catch sb off guard
chū qí bù yì gōng qí bù bèi
catch an enemy off guard with a surprise attack (idiom, from Sunzi's Art of War 孫子兵法|孙子兵法)
chū qí bù yì , gōng qí bù bèi
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[Sun1 zi3 Bing1 fa3])