 Qin then used its connections along the Yangtze River the Xiang River to expand China into Hunan, Jiangxi and Guangdong, setting up military commanderies along the main lines of communication.At the collapse of the Qin Dynasty, these southern commanderies became the independent Nanyue Empire under Zhao Tuo while Chu and Han vied with each other for control of the north.From the Han dynasty, the region of the Yangtze River became more and more important to China's economy.