七国之乱
After Crown Prince Qi became emperor (as Emperor Jing) in 157 BC, a military emergency did arise. Concerned that the princes of collateral lines of the imperial clan were becoming overly powerful, Emperor Jing, based on the advice of Chao Cuo, attempted to reduce the size of the principalities. Seven principalities, led by the powerful principalities of Wu (modern southern Jiangsu, northern Zhejiang, southern Anhui, and northern Jiangxi) and Chu (modern northern Jiangsu and northern Anhui) rebelled in a war later known as the Rebellion of the Seven States.