Empire. Jin rulers attempted to develop this region as a centre of rule and as a base for the reconquest of their homeland. Jin rulers granted large tracts of land in the south to Chinese immigrants and landowners fleeing barbarian rule, who preserved the system of government that was in place before the uprising. The migration of northern people stimulated the southern economy, allowing it to rival the northern economy. Improved agricultural techniques introduced to the south increased production and a market economy survived as Jin rulers enforced laws. The improvement of the southern economy can be seen later when it financed Liu Yu's expeditions to recover Sichuan and most of the Chinese heartland from the barbarian states of the north. Southern and Northern Dynasties (420–581) The Southern and Northern Dynasties, despite constant war, largely recovered from the Wu Hu uprising. The early part of the era saw the greater part of China reunified by the native Liu Song dynasty, whose northern border extended to the Yellow River. The Liu Song founder and general, Liu Yu, reclaimed much of China's heartland, conquering most of the states that the Wu Hu had established in the 4th century, excluding the Xianbei state of Northern Wei. Under his son, China witnessed a brief period of prosperity during the Yuanjia era. However, a later Xianbei invasion once more confined the Chinese dynasties to the territories south of the Huai River. Henceforth, China was divided into the Northern and Southern dynasties, which developed separately; the north prospering under a new equal-field system, while the southern economy continued to develop in the fashion of Wei and Jin. In 589, the Sui dynasty restored native rule to northern China and reunified the country. Southern Dynasties The Yuanjia era, inaugurated by Liu Yu and his son, Emperor Wen, was a period of prosperous rule and economic growth, despite ongoing war. Emperor Wen was known for his frugal administration and his concern with the welfare of the people. Although he lacked the martial power of his father, he was an excellent economic manager. He reduced taxes and levies on peasants and encouraged them to settle in areas that had been reconquered by his father. He reduced the power of wealthy landowners and increased the taxable population. He also enacted a system of reviewing the performance of civil servants. As a result of his policies, China experienced an era of