Duke Mu of Cao (8th Century BCE) () was the eleventh ruler of the vassal State of Cao during the Chinese Eastern Zhou dynasty (770 â 256 BCE) and Spring and Autumn period. Born Jë Wà(姬æÂ¦), he was the son of Cáo Huìbó (æÂ¹æÂ ä¼¯). In 760 BCE, Duke Mu of Cao killed his elder brother Cáo Fèibó (æÂ¹å»¢ä¼¯/æÂ¹åºÂ伯) and appointed himself ruler of the State of Cao. He was the first ruler of the State of Cao to receive the posthumous title of "Duke" (å ¬).