The courts at Nanjing repeatedly had to deal with challenges to their authority. The most destructive uprising began in 548, initiated by a would-be warlord from the north, Hou Jing, who gathered a huge army of disaffected and set siege to the capital. By the time the city fell four months later, many members of the great families had starved to death in their mansions. Although a general soon declared a new dynasty (Chen), his control over outlying areas amounted to little more than the privilege of confirming local strongmen as his governors.

Meanwhile, the north was following a different trajectory. In the fourth century, rival warlord of many different ethnic groups fought for control, ousting each other whenever they could. The first to secure their position by finding ways to draw on the wealth of China's settled agriculture was the Tuoba clan of the Xianbei who established the (Northern) Wei dynasty (439-534). Originally from southern Manchuria, by the early fourth century the Xianbei occupied land in northern Shanxi province, which they used as a base to raid other tribes and Chinese settlements, bringing back captives, horse cattle, and sheep. As they expanded into Chinese territory, they forced massive relocations of population to bring deserted land back into cultivation and to supply the capital they built. In their desire to preside over the whole Chinese world, they turned to educated Chinese as experts in statecraft. It was expedient for them to employ Chinese officials and adopt the institutions they proposed, because the total number of Xianbei and other northern tribesman in their confederation could not have been more than a couple of million, but the Chinese, over whom they were trying to maintain military control, numbered twenty or thirty million or more.

It was on Chinese advice that in 486 the Northern Wei government undertook a major overhaul of its fiscal system, instituting an "equal field" system reminiscent of Han efforts to tax individual cultivators and Cao Cao's military colonies and state lands. The Wei system was based on the premise that the state owned all land. Individual families were to be assigned 20 mu of permanent, inheritable land for growing mulberry and other trees plus lifetime allotments of crop land, the amount depending on their available labour; for instance 40 mu was allocated per able-bodied man (including slaves) and 30 per ox. Larger landholdings were only to be allowed for the families of officials. The memorial proposing this 'equal field' system argued that it would 'ensure that no land lies neglected, that no people wander off, that powerful families could not monopolize the fertile fields, and that humble people would also get their share of the land', Even if the powerful were usually able to manoeuvre=maneuver around the law, the government had asserted its power to assign and tax land, a key step towards building a fiscal base for a more intrusive form of government.