He was well known for his opposition to French involvement in Vietnam, completing the final Vietnamese conquest of Champa, temporary annexation of Cambodia, and his rigid Confucian orthodoxy.

At the age of three, under the effect of a written agreement made by Gia Long with his first wife the Empress Thừa Thiên, she took Đảm in and raised him as her own son.

[3] Following Thừa Thiên's death in 1814, it was supposed that her grandson, Crown Prince Cảnh's eldest son Mỹ Đường, would be responsible for conducting the funeral.

After the ceremony, Crown Prince Đảm moved to Thanh Hòa Palace and started assisting his father in processing documents and discussing country issues.

In the early years of Minh Mạng's government, the most serious challenge came from one of his father's most trusted lieutenants and a national hero in Vietnam, Lê Văn Duyệt, who had led the Nguyễn forces to victory at Qui Nhơn in 1801 against the Tây Sơn dynasty and was made regent in the south by Gia Long with full freedom to rule and deal with foreign powers.

After strong lobbying by Duyệt, the governor of Cochin China, and a close confidant of Gia Long and Pigneau de Behaine, Minh Mạng agreed to release the priests on the condition that they congregate at Đà Nẵng and return to France.

Nevertheless, Napoleon had seen Vietnam as a strategically important objective in the Anglo-French power struggle in Asia, as he felt that it would make an ideal base from which to contest the East India Company's foothold in the Indian subcontinent.

With the restoration of the Bourbon monarchy and the final exile of Napoleon in 1815, the military scene in Europe quieted and French interest in Vietnam was revived.

The policy of isolationism soon saw Vietnam fall further behind the pace of technology and become more vulnerable to outside encroachment as political stability returned to continental Europe, allowing European powers free hand to once again direct their attention towards increasing their influence in Asia.

[citation needed] In 1819, Lieutenant John White of the United States Navy was the first American to make contact with Vietnam, arriving in Saigon.

It was assumed that the snub was related to an attempt by Bougainville to smuggle ashore a Catholic missionary from the Missions étrangères de Paris.

President Andrew Jackson tried twice to contact Minh Mạng, sending Edmund Roberts in 1832, and Consul Joseph Balestier in 1836, to no avail.

In 1837 and 1838, La bonite and L'Artémise were ordered to land in Tourane to attempt to gauge the situation in Vietnam with respect to missionary work.

Minh Mang saw a risky war against Siam, the former ally, might have jeopardized Vietnamese hegemony in Cambodia, which had been acquired by his father Gia Long.

Minh Mạng was forced to put down a Siamese attempt to regain control of the vassal, as well as an invasion of southern Vietnam which coincided with rebellion by Lê Văn Khôi.

Eventually, Minh Mạng's forces were able to repel the invasion, as well as the revolt in Saigon, and he reacted to Western encroachment by blaming Christianity and showing hostility, leading to the European powers' asserting that intervention was needed to protect their missionaries.

This resulted in missed opportunities to avert the colonisation of Vietnam through having friendly relations, since strong opposition was raised in France against an invasion, due to the costs of such a venture.

After the outbreak of the First Opium War in 1839, Minh Mạng attempted to build an alliance with European powers by sending a delegation of two lower rank mandarins and two interpreters in 1840.

In 1839, Minh Mạng introduced a program of salaries and pensions for princes and mandarins to replace the traditional assignment of fief estates.

[13] Despite ongoing intra-turmoil, Minh Mang exhibited his admiring to Confucian rule and classical Chinese culture, while imposing ethnic assimilation at home[14][15] and pursuing territorial expansion and interference in neighboring Laos.

Minh Mang put his support to Vientiane's king Chao Anou, his close ally, to wage war against Siam.

Anou was defeated and then was detaining to the Siamese in late 1828 by Chao Noi, ruler of Muang Phuan, also a tributary of Minh Mang.

The Minh hương were South Chinese refugees of the Ming dynasty that had migrated and settled down in South Vietnam earlier during the 17th century, who married with Cambodian women, had been substantially assimilated to local Vietnamese and Khmer populaces, and loyal to the Nguyen, compared to the Thanh nhân, Chinese immigrants of the Qing dynasty that recently arrived in Southern Vietnam, who dominated the grain trade.

Douglas Johnson recalled year 1836 as the momentum marked the greatest territorial extent of the Vietnamese empire, also high point of its stability which most revolts in Minh Mang's realm had been suppressed.

[26] However, continuous uprisings in Cambodia, Tonkin, and wars with Siam put Minh Mang's expansion to an query, as all sides became exhausted.

Historical opinion is divided with scholars contesting whether the grave desecration or the loss of southern autonomy after Duyệt's death was the main catalyst.

Khôi's rebels brought Cochinchina under their control and proposed to replace Minh Mạng with a son of Prince Cảnh.

The first French missionary executed was Gagelin in October 1833, the second was Marchand, who was put to death along with the other leaders of the Saigon citadel which surrendered in September 1835.

When Minh Mạng died, he left the throne to his son, Emperor Thiệu Trị, who was more rigidly Confucianist and anti-imperialist than his father.

Nevertheless, during his reign, Minh Mạng had established a more efficient government, stopped a Siamese invasion and built many national monuments in the imperial city of Huế.