Cao

Cao was a small earldom of the central plain, remembered less for power than for the statesmen it lent to greater powers. Founded by Cao Shuzhenduo, son of King Wen of Zhou, with its capital at Taoqiu near modern Dingtao, Cao held a few cities between Song and Lu and survived by careful deference: when its duke quarrelled with his own officers, it was Duke Huan of Qi who restored him. The state's poverty of land was made up in men, and Cao exiles served as ministers in the courts of greater powers. In the struggles of the fifth century BC the buffer states were the first eaten: Song, grown ambitious under its own kings, coveted the Taoqiu markets, and in 487 BC Song troops took the capital, divided the land, and ended Cao's five and a half centuries. The earldom that had survived by being useful to everyone fell when its neighbours no longer needed a go-between.