The degenerated Le dynasty, which endured under ten rulers between 1497 and 1527, in the end was no longer able to maintain control over the northern part of the country, much less the new territories to the south. The weakening of the monarchy created a vacuum that the various noble families of the aristocracy were eager to fill. In 1527 Mac Dang Dung, a scholar-official who had effectively controlled the Le for a decade, seized the throne, prompting other families of the aristocracy, notably the Nguyen and Trinh, to rush to the support of the Le. An attack on the Mac forces led by the Le general Nguyen Kim resulted in the partition of Vietnam in 1545, with the Nguyen family seizing control of the southern part of the country as far north as what is now Thanh Hoa Province. The Nguyen, who took the hereditary title chua (see Glossary), continued to profess loyalty to the Le dynasty. By the late sixteenth century the Trinh family had ousted the Mac family and had begun to rule the northern half of the country also in the name of the Le dynasty. The Trinh, who, like the Nyuyen, took the title chua, spent most of the seventeenth century attempting to depose the Nguyen. In order to repulse invading Trinh forces, the Nguyen in 1631 completed the building of two great walls, six meters high and eighteen kilometers long, on their northern frontier. The Trinh, with 100,000 troops, 500 elephants, and 500 large junks, were numerically far superior to their southern foe. The Nguyen, however, were better equipped, having by this time acquired Portuguese weapons and gunpowder, and, as the defending force, had the support of the local people. In addition, the Nguyen had the advantage of controlling vast open lands in the Mekong Delta, wrested from the Khmer, with which to attract immigrants and refugees from the north. Among those who took up residence in the delta were an estimated 3,000 Chinese, supporters of the defunct Ming dynasty, who arrived in 1679 aboard fifty junks and set about becoming farmers and traders. The Nguyen, aided by the Chinese settlers, succeeded in forcing the Khmer completely out of the Mekong Delta by 1749.

After major offensives by the Trinh in 1661 and 1672 foundered on the walls built by the Nguyen, a truce in the fighting ensued that lasted nearly 100 years. During that time, the Nguyen continued its southward expansion into lands held, or formerly held, by the Cham and the Khmer. The Trinh, meanwhile, consolidated its authority in the north, instituting administrative reforms and supporting scholarship. The nobility and scholar-officials of both north and south, however, continued to block the development of manufacturing and trade, preferring to retain a feudal, peasant society, which they could control.

The seventeenth century was also a period in which European missionaries and merchants became a serious factor in Vietnamese court life and politics. Although both had arrived by the early sixteenth century, neither foreign merchants nor missionaries had much impact on Vietnam before the seventeenth century. The Portuguese, Dutch, English, and French had all established trading posts in Pho Hien by 1680. Fighting among the Europeans and opposition by the Vietnamese made the enterprises unprofitable, however, and all of the foreign trading posts were closed by 1700.

European missionaries had occasionally visited Vietnam for short periods of time, with little impact, beginning in the early sixteenth century. The best known of the early missionaries was Alexandre de Rhodes, a French Jesuit who was sent to Hanoi in 1627, where he quickly learned the language and began preaching in Vietnamese. Initially, Rhodes was well-received by the Trinh court, and he reportedly baptized more than 6,000 converts; however, his success probably led to his expulsion in 1630. He is credited with perfecting a romanized system of writing the Vietnamese language (quoc ngu), which was probably developed as the joint effort of several missionaries, including Rhodes. He wrote the first catechism in Vietnamese and published a Vietnamese-Latin-Portuguese dictionary; these works were the first books printed in quoc ngu. Quoc ngu was used initially only by missionaries; classical Chinese or chu nom continued to be used by the court and the bureaucracy. The French later supported the use of quoc ngu, which, because of its simplicity, led to a high degree of literacy and a flourishing of Vietnamese literature. After being expelled from Vietnam, Rhodes spent the next thirty years seeking support for his missionary work from the Vatican and the French Roman Catholic hierarchy as well as making several more trips to Vietnam.

The stalemate between the Trinh and the Nguyen families that began at the end of the seventeenth century did not, however, mark the beginning of a period of peace and prosperity. Instead the decades of continual warfare between the two families had left the peasantry in a weakened state, the victim of taxes levied to support the courts and their military adventures. Having to meet their tax obligations had forced many peasants off the land and facilitated the acquisition of large tracts by a few wealthy landowners, nobles, and scholar--officials. Because scholar--officials were exempted from having to pay a land tax, the more land they acquired, the greater was the burden that fell on those peasants who had been able to retain their land. In addition, the peasantry faced new taxes on staple items such as charcoal, salt, silk, and cinnamon, and on commercial activities such as fishing and mining. The disparate condition of the economy led to neglect of the extensive network of irrigation systems as well. As they fell into disrepair, disastrous flooding and famine resulted, unleashing great numbers of starving and landless people to wander aimlessly about the countryside. The widespread suffering in both north and south led to numerous peasant revolts between 1730 and 1770. Although the uprisings took place throughout the country, they were essentially local phenomena, breaking out spontaneously from similar local causes. The occasional coordination between and among local movements did not result in any national organization or leadership. Moreover, most of the uprisings were conservative, in that the leaders supported the restoration of the Le dynasty. They did, however, put forward demands for land reform, more equitable taxes, and rice for all. Landless peasants accounted for most of the initial support for the various rebellions, but they were often joined later by craftsmen, fishermen, miners, and traders, who had been taxed out of their occupations. Some of these movements enjoyed limited success for a short time, but it was not until 1771 that any of the peasant revolts had a lasting national impact.

Data as of December 1987