As a high-ranking military commander residing in the capital, he had all opportunities to seize power during the tumultuous years after Emperor Le Hoan's death, yet preferring not to do so out of his sense of duty. He was in a way being "elected" by the court after some debate before a consensus was reached.

Ly Cong Uan, posthumously referred as Ly Thyi To, changed the country's name to Đai Viet, "Great Viet". The Ly Dynasty is credited for laying down a concrete foundation, with strategic vision, for the nation of Vietnam. Leaving Hoa Lu, a natural fortification surrounded by mountains and rivers, Ly Công Uan moved his court to the new capital in present-day Hanoi and called it Thang Long (Ascending Dragon). Ly Cong Uan thus departed from the militarily defensive mentality of his predecessors and envisioned a strong economy as the key to national survival. Successive Ly kings continued to accomplish far-reaching feats: building a dike system to protect the rice producing area; founding Quốc Tử Giám, the first noble university; holding regular examinations to select capable commoners for government positions once every three years; organizing a new system of taxation; establishing humane treatment of prisoners. Women were holding important roles in Ly society as the court ladies were in charge of tax collection. The Ly Dynasty also promoted Buddhism, yet maintained a pluralistic attitude toward the three main philosophical systems of the time: Buddhism, Confucianism, and Taoism. During the Ly Dynasty, the Chinese Song Dynasty officially recognized the Dai Viet monarch as King of Giao Chi (Giao Chi Quan Vương).

The Ly Dynasty had two major wars with Song China, and a few conquests against neighboring Champa in the south. Most notable Song-Ly battle took place on Chinese land in 1075 AD. Upon learning that a Song invasion was imminent, the Ly army and navy (about 100,000 men) under the command of Ly Thuong Kiet, Tong Dan used amphibious operations to preemptively destroy three Song military installations at Yong Zhou, Qin Zhou, and Lian Zhou in present-day Guangdong and Guangxi, and killed 100,000 Chinese. The Song Dynasty took revenge and invaded Dai Viet in 1076 CE yet Song troops were held back at the Battle of Như Nguyệt River (commonly Cầu river), now in Bắc Ninh province (about 40 km from the current capital, Hanoi). As neither side could win, the Lý Dynasty proposed a truce, which the Song Dynasty accepted.

Toward the end of the Ly Dynasty, a powerful court minister named Tran Thu Đo forced king Ly Hue Tong to become a Buddhist monk and Ly Chieu Hoang, Hue Tong's young daughter, to become queen. Tran Thu Đo then arranged the marriage of Chieu Hoang to his nephew Trần Cảnh and eventually had the throne transferred to Tran Canh, thus begun the Tran Dynasty. Tran Thu Do viciously purged members of the Ly nobility; some Ly princes escaped to Korea, being thought to be the first political exiles in Vietnamese history (see Ly Long Tuong).

Although Tran Thu Do had purged members of Ly nobility, most Tran kings ruled the country in similar manner to the Ly kings. Noted Tran Dynasty accomplishments include the creation of a system of population records based at the village level, the compilation of a formal 30-volume history of Đai Viet by Lê Văn Hưu, and the rising in status of the Nom script, a system of writing for Vietnamese language. The Trần Dynasty also adopted a unique way to train new kings: as a king aged, he would relinquish the throne to his crown prince, yet holding a title of August Higher Emperor, acting as a mentor to the new Emperor.

Mongol invasions

During the Tran Dynasty, Đai Viet repelled three invasions (in 1257 AD, 1284 AD, and 1288 AD) by the Mongols under Kublai Khan, who had occupied China and founded the Yuan dynasty (see Mongol invasions of Vietnam). The key to Dai Viet's successes was to avoid the Mongols' strength in open field battles and city sieges (the Trần court abandoned the capital and the cities), then countered them decisively at their weak points, which were battles in swampy areas (such as Chuong Duong, Ham Tu, Van Kiep) and on rivers (such as Van Don and Bach Dang). The Mongols also suffered from tropical diseases and loss of supplies to Tran army's raids. The Yuan-Tran war reached its climax when retreating Yuan fleet was decimated at the Battle of Bach Dang (1288). The military architect behind Dai Viet's victories was Commander Trần Quốc Tuấn, more popularly known as Tran Hung Dao.

Champa

It was also during this period that the Tran kings waged many wars against the southern kingdom of Champa, continuing the Viets' long history of southern expansion (known as Nam Tien) that had begun shortly after gaining independence from China. Often, they encountered strong resistance from the Chams. Champa troops led by king Chế Bồng Nga (Cham: Po Binasuor or Che Bonguar) killed king Trần Duệ Tông in battle and even laid siege to Đai Viet's capital Thang Long in 1377 AD and again in 1383 AD. However, the Tran Dynasty was successful in gaining two Champa provinces, located around present-day Hue, through the peaceful means of the political marriage of Princess Huyền Tran to a Cham king.

Ming occupation and the rise of the Le dynasty

The Tran dynasty was in turn overthrown by one of its own court officials, Ho Quy Ly. Ho Quy Ly forced the last Tran king to resign and assumed the throne in 1400. He changed the country name to Dai Ngu and moved the capital to Tay Do, Western Capital, now Thanh Hoa. Thang Long was renamed Dong Do, Eastern Capital. Although widely blamed for causing national disunity and losing the country later to the Chinese Ming Dynasty, Ho Quy Ly's reign actually introduced a lot of progressive, ambitious reforms, including the addition of mathematics to the national examinations, the open critique of Confucian philosophy, the use of paper currency in place of coins, the investment in building large warships and cannons, and land reform. He ceded the throne to his son, Ho Han Thuong, in 1401 and assumed the title Thai Thuong Hoang, in similar manner to the Tran kings.

In 1407, under the pretext of helping to restore the Tran Dynasty, Chinese Ming troops invaded Dai Ngu and captured Ho Quy Ly and Ho Han Thuong. The Ho dynasty came to an end after mere 7 years in power. The Ming occupying force annexed Dai Ngu into the Ming Empire after claiming that there was no heir to Tran throne. Almost immediately, Trần loyalists started a resistance war. The resistance, under the leadership of Tran Qui, at first gained some advances, yet as Tran Qui executed 2 top commanders out of suspicion, a rift widened within his ranks and resulted in his defeat in 1413.

In 1418, a wealthy farmer, Le Loi, led the Lam son revolution against the Ming from his base of Lam Son (Thanh Hoa province). Overcoming many early setbacks and with strategic advice from Nguyen Trai, Lê Lợi's movement finally gathered momentum, marched northward, and launched a siege at Đong Quan (now Hanoi), the capital of the Ming occupation. The Ming Emperor sent a reinforcement force, but Le Loi staged an ambush and killed the Ming commander, Lieu Thang (Chinese: Liu Sheng), in Chi Lang. Ming troops at Dong Quan surrendered. The Lam son revolution killed 300,000 Ming soldiers. In 1428, Lê Lợi ascended to the throne and began the Hau Le dynasty (Posterior Le). Le Loi renamed the country back to Dai Viet and moved the capital back to Thang Long.

Map of Vietnam showing the conquest of the south (the Nam Tien, 1069-1757).The Le Dynasty carried out land reforms to revitalize the economy after the war. Unlike the Lý and Trần kings, who were more influenced by Buddhism, the Lê kings leaned toward Confucianism. A comprehensive set of laws, the Hồng Đức Code was introduced with some strong Confucian elements, yet also included some progressive rules, such as the rights of women. Art and architecture during the Lê Dynasty also became more influenced by Chinese styles than during the Ly and Tran Dynasty. The Le Dynasty commissioned the drawing of national maps and had Ngo Si Lien continue the task of writing Dai Viet's history up to the time of Le Loi. King Le Thanh Tong opened hospitals and had officials distribute medicines to areas affected with epidemics.

In 1471, Le troops led by king Le Thanh Tong invaded Champa and captured its capital Vijaya. This event effectively ended Champa as a powerful kingdom, although some smaller surviving Cham kingdoms still lasted for a few centuries more. It initiated the dispersal of the Cham people across Southeast Asia. With the kingdom of Champa mostly destroyed and the Cham people exiled or suppressed, Vietnamese colonization of what is now central Vietnam proceeded without substantial resistance. However, despite becoming greatly outnumbered by Kinh (Viet) settlers and the integration of formerly Cham territory into the Vietnamese nation, the majority of Cham people nevertheless remained in Vietnam and now considered one of the key minorities in modern Vietnam. (The modern city of Hue, founded in 1600 lies close to where the Champa capital of Indrapura once stood). In 1479, king Le Thanh Ton also campaigned against Laos and captured its capital Luang Phrabang.