In order to facilitate administration of their new territories, the Chinese built roads, waterways, and harbors, largely with corves labor (unpaid labor exacted by government authorities, particularly for public works projects). Agriculture was improved with better irrigation methods and the use of ploughs and draft animals, innovations which may have already been in use by the Vietnamese on a lesser scale. New lands were opened up for agriculture, and settlers were brought in from China. After a few generations, most of the Chinese settlers probably intermarried with the Vietnamese and identified with their new homeland.
The first and second centuries A.D. saw the rise of a HanViet ruling class owning large tracts of rice lands. More than 120 brick Han tombs have been excavated in northern Vietnam, indicating Han families that, rather than returning to China, had become members of their adopted society and were no longer, strictly speaking, Chinese. Although they brought Chinese vocabulary and technical terms into their new culture, after a generation or two, they probably spoke Vietnamese.
The second century A.D. was a time of rebellion in Giao Chi, Cuu Chan, and Nhat Nam, largely due to the declining quality of the Han administrators, who concentrated their energies on making their fortunes and returning north as soon as possible. Revolts against corrupt and repressive Chinese officials were often led by the Han-Viet families. The fall of the Han dynasty in China in 220 A.D. further strengthened the allegiance of the Han-Viet ruling elite to their new society and gave them a sense of their own independent political power. Meanwhile, among the peasant class there was also a heightened sense of identity fostered by the spread of Buddhism by sea from India to Vietnam by the early third century. The new religion was often adapted to blend with indigenous religions. Buddhist temples were sometimes dedicated to the monsoon season, for example, or identified with the guardian spirit of agricultural fertility. Although ruling-class Vietnamese tended to cling to Confucianism, various local rulers patronized the Buddhist religion, thus helping to legitimize their own rule in the eyes of the common people.
After the demise of the Han dynasty, the period of the third to the sixth century was a time of turbulence in China, with six different dynasties in succession coming to power. The periods between dynasties or the periods when dynasties were weak in China were usually the most peaceful in Vietnam. When dynasties were strong and interfered with local rule, the Vietnamese aristocracy engaged in a series of violent revolts that weakened China's control over its southern territory. A rebellion led by the noblewoman Trieu Au (Lady Trieu) in A.D. 248 was suppressed after about six months, but its leader earned a place in the hearts and history of the Vietnamese people. Despite pressure to accept Chinese patriarchal values, Vietnamese women continued to play an important role and to enjoy considerably more freedom than their northern counterparts.