In the 3rd century BC, the Han people who lived in the Yellow River basin unified China, merging the various ethnic groups who lived in southern China to the south of the Yangtze River into a centralized empire. This feudal empire soon spread southwards.
In 111 B.C. the Han dynasty sent an expeditionary corps to conquer the kingdom of Nam Viet established by Chao To, who had brought the kingdom of Au Lac and several territories in southern China together under his rule. The Han integrated Au Lac into their empire, creating the commandery of Chiao Chih, which was divided into provinces and districts. The three provinces, which constituted present-day northern Vietnam to the 18th parallel, had a population of 981, 375 people according to Han documents. From this time on, the history of Vietnam evolved under the combined influence of two contradictory factors. On the one hand, there was a policy of' economic exploitation and cultural assimilation, and on the other, there was a steadfast popular resistance marked by armed insurrection against foreign domination. A final resistance led to the preservation of the identity of the Vietnamese people after many centuries, the emergence of a national consciousness, and the establishment of the independent state of Vietnam. While keeping its unique character, the nation's culture also adopted quite a few elements of Chinese culture. Ten centuries of domination resulted in a thorough transformation of Vietnamese society.
At first, for their own benefit, the Han retained the system of lac hau and lac tuong, the civilian and military chiefs of the early communities; little by little, they replaced them with functionaries appointed by the court who administered the country down to province and district levels (there were three provinces and 56 districts). A mandarin, protected by an armed entourage, presided over each district. The rural communes, which contained most of the population, escaped their direct rule so that this administration very slowly expanded its network throughout the country while coping with a stubborn popular resistance. The imperial functionaries came from China, accompanied by an entourage of scribes, agents and family members. Many of them settled in the country permanently
The population had to make a double contribution: a tribute to the imperial court and taxes, duties and corvee to maintain the administration and military apparatus. The tribute paid to the court mostly comprised valuable tropical products such as ivory, mother-of-pearl, pearls and sandalwood which Chinese documents of the time described as abundant and varied products from the southern territories. Tropical fruit, various handicraft items, fabric, gold or silver engravings, and mother-of-pearl inlay work were also required. A certain number of craftsmen were exiled to work for the court while part of the population was compelled to hunt for elephant and rhinoceros in forests or dive into the sea to gather pearls or coral.
Each inhabitant had to pay a head-tax and a land tax on each plot; the population was also forced to supply corvee labourers to dig canals and build roads and citadels. Chinese documents describe many revolts due to this systematic exploitation and extortion by imperial functionaries.
At the same time, the feudal Han carried out a policy of systematic cultural assimilation, the empire having to be unified in all aspects. The first concern was to impose veneration of the emperor, Son of Heaven; use of the indeographic script was enforced as a vehicle for the official doctrine, Confucianism. At the centre of human obligation was absolute loyalty to the monarch, who ruled not only human society but also the kingdom of the gods. A tightly-woven network of obligations and rites bound societal and individual life, strictly governing relationships between parents and children, husbands and wives, between friends, and between subjects and the imperial administration which tried to replace old customs with laws and rites inspired by Confucian doctrine.
Economic exploitation by the occupiers hampered the development of productive forces but could not check them. Excavation of tombs dating from the 1st to the 6th centuries has revealed the progressive diffusion of iron tools, production implements and weapons already known in the previous era. Iron cauldrons, nails and tripods appeared while objects in bronze became less common, although the making of bronze drums continued for centuries.
In the 1st century, furrowing with iron ploughshares on wingploughs drawn by oxen or water buffaloes gradually replaced cultivation in burned out clearings. In particular, hydraulic works, canals and dykes ensured control over water; the use of fertilizer facilitated intensive farming, the practice of growing two crops a year on well-irrigated fields for example. The growing of tubers such as sweet potato, sugarcane and mulberry was already known, as well as various vegetables and fruit trees. Mulberry growing and silkworm raising took pride of place; there was also betel, areca-nut trees, medicinal plants, bamboo and rattan, which supplied raw materials for basket making. From the earliest centuries, there was thus a diversified agriculture which, gradually improved, would last for a very long time.
Handicrafts also reached a relatively high level. Many tools of iron and bronze were forged; ceramics with enamel coating was added to the already flourishing pottery of the previous era. The remains of citadels, pagodas and tombs showed that brick and tile making was thriving, some of which were also coated with a layer of enamel.
The most prosperous handicraft occupations were weaving and basket-making. Fabrics in cotton and silk and baskets of bamboo and rattan were sought after items. In the 3rd century, paper began to be made using techniques imported from China. Glass-making techniques also came to Vietnam from China and India. To meet the need for luxury goods for the court and local functionaries, the making of objects in engraved gold and silver underwent new development, the quality of which improved through the use of Chinese techniques. Lacquer was already known. It could be said that Vietnamese handicrafts established themselves during this period.
If the economy as a whole remained autarkic, certain products supplied markets in administrative centres such as Long Bien (in present-day Hanoi Capital) which had trading quarters. River and sea transport was carried out using sampans or junks, some of which had barges and several score oarsmen. The Red River and the road running along it led to Yunnan and Sichuan, and hence to Central Asia as well as Burma. Communication with China was achieved by both sea and land, the road being dotted with many relays. Chiao Chih served as a port of call for junks from Java, Burma, Iran, India and even the Roman empire on their way to China. In large centres, there were a number of foreign residents such as Khmers and Indians. The vessels carried local products, valuable timbers, ivory and handicrafts, and also took part in the slave trade. This external trade was entirely monopolized by the occupiers.
The Han policy of cultural assimilation benefited from the prestige of Chinese civilization, , which was then at a high level, but it was confronted with a stubborn resistance. The Vietnamese language was largely borrowed from Chinese, but the words had been Vietnamized to become part and parcel of the language which was progressively enriched without losing its identity; popular literature kept its vigour while beginning to develop a learned literature written in Han (classical Chinese). Despite Confucian rites and precepts, many local traditions continued the veneration of founding fathers or patriots, participation by women in patriotic activities, and the making and use of bronze drums during great ceremonies. Relics found in the tombs of that era show stronger Han civilization influence; the indigenous upper classes came under greater foreign influence than the population at large or rural communities. However, Dong Son art was still clearly seen with its decorations and statuettes.
Together with Confucianism, Buddhist and Taoist doctrine also made their way into Chiao Chih. Buddhism, coming from India by sea and from China by land, was conspicuous from the 2nd and 6th centuries, with the town of Luy Lau (in present-day Bac Ninh Province) having 20 towers, 500 bonzes and 15 already-translated sutras. Taoism integrated itself with local beliefs, giving rise to magical, medical and ascetic practices. The main characteristic of these religions was that they did not encourage fanaticism nor exclude one another, thus helping to preserve unity within the national community.
Following the conquest by the Han, Vietnamese society gradually turned into a feudal society. De jure, land belonged entirely to the emperor, while all members of the population became his subjects, bound to pay taxes, corvee and other duties. Nevertheless, the communes stayed more or less autonomous. To ensure domination, the Han feudalists advocated the creation of "military colonies"; military men, political or common-law prisoners and destitute people coming from China together with destitute Vietnamese and landless peasants were recruited to reclaim and exploit the land under the direction of officers or functionaries. At the same time, private domains were created by Chinese functionaries settled for good in the country or indigenes loyal to the administration (members of the former ruling classes or notables from rural communities). After the 2nd century, a certain number of Vietnamese who had received a good education had access to mandarin posts and, hence, could set up private domains. Slaves worked in these military colonies and domains. The tombs of that era often reveal models in baked earth of domains with outer areas dotted with watchtowers, houses, granaries and stables. As time went by, the Chinese functionaries and their descendants living in the country became "Vietnamized". With indigenous functionaries and landowners, they constituted an indigenous ruling class with feudal characteristics.
Shaped in a country subject to the harsh domination of the Han imperialists, this feudal class was opposed in some aspects to the court and sided with the population. Internal disturbances in China, caused mostly by peasant revolts, created favourable conditions for an open struggle against Chinese imperialist domination for secession - first temporary, then definitive.