The Three Qins refer to three of the 19 principalities created by Xiang Yu in the aftermaths of the collapse of Qin Dynasty in 206 BC. Now "Three Qins" is another name for Shaanxi Province in China.
Originally, according to the pledge made by Mi Xin, , Qin proper should have been given to Liu Bang, because Liu entered Qin proper first. However, Xiang Yu, jealous and fearful of Liu's accomplishment, effectively exiled Liu by giving him the Principality of instead. Xiang instead divided Qin proper into three principalities, which he awarded to three former Qin military leaders:
, given to Qin general , who had been forced to surrender to Xiang, occupying modern central Shaanxi;
, given to Zhang Han's deputy Sima Xin , occupying modern northeastern Shaanxi;
, given to Zhang Han's assistant Dong Yi , occupying modern northern Shaanxi.
Xiang, however, either did not realize or ignored that the people of Qin despised Zhang, Sima, and Dong, for having been sole survivors of Xiang's massacre of Qin forces that Zhang had surrendered to Xiang.
In autumn 206 BC, Han forces, led by Liu's general Han Xin, made a surprise attack against the three Qins and easily conquered them. Sima and Dong surrendered quickly. Zhang was sieged in his capital of Feiqiu for nearly a year, and finally committed suicide in summer 205 BC. Feiqiu then surrendered.