Early years

Born in Phú Xuân (modern-day Huế, central Vietnam) on 8 February 1762, he also had two other names in his childhood: Nguyễn Phúc Chủng (阮福種) and Nguyễn Phúc Noãn (阮福暖). Nguyễn Ánh was the third son of Nguyễn Phúc Luân and Nguyễn Thị Hoàn. Luan was the second son of Lord Nguyễn Phúc Khoát of southern Vietnam; the first son had already predeceased the incumbent Lord. There are differing accounts on which son was the designated successor. According to one theory, Luân was the designated heir, but a high-ranking mandarin named Trương Phúc Loan changed Khoat's will of succession on his deathbed, and installed Luan's younger brother Nguyễn Phúc Thuần, the sixteenth son, the throne in 1765. Luan was jailed and died in the 1765, the same year as Thuan's installation. However, the historian Choi Byung Wook claims that the notion that Luân was the designated heir was based on fact but was propagated by 19th century Nguyễn Dynasty historians after Nguyễn Ánh had taken the throne as Gia Long to establish the emperor's legitimacy. According to Choi, Lord Khoát had originally chosen the ninth son, who then died, leaving Loan to install Lord Thuần. At the time, the alternative was the eldest son of the ninth son, Nguyễn Phúc Dương, whom opposition groups later tried unsuccessfully to convince to join them as a figurehead to lend legitimacy. In 1775, Thuan was forced to share power with Dương by military leaders who supported the Nguyêns. At this time, Nguyễn Ánh was a minor member of the family and did not have any political support among court powerbrokers.

However, Thuan lost his position as lord of southern Vietnam and was killed, along with Duong, during the Tây Sơn rebellion led by the brothers Nguyễn Nhạc, Nguyễn Huệ and Nguyễn Lữ in 1777. Nguyễn Ánh was the most senior member of the ruling family to have survived the Tây Sơn victory, which pushed the Nguyễn from their heartland in central Vietnam, southwards towards Saigon and into the Mekong Delta region in the far south. This turn of events changed the nature of the Nguyễn power hierarchy; the family and the first leader Nguyễn Hoàng had originally come from Thanh Hoa Province in northern Vietnam, and this is where most of their senior military and civil leadership's heritage derived from, but as a result of the Tây Sơn's initial successes, much of this old power base was destroyed and Nguyễn Ánh had to rebuild his support network among southerners, who later became the core of the regime when the Nguyễn Dynasty was established.

Nguyễn Ánh was sheltered by a Catholic priest Paul Nghi (Phaolô Hồ Văn Nghị) in Rạch Giá. Later, he fled to Hà Tiên on the southern coastal tip of Vietnam, where he met Pigneau de Behaine, a French priest who became his adviser and played a major part in his rise to power. Receiving information from Paul Nghi, Pigneau avoided the Tay Son army in Cambodia, and came back to assist Nguyễn Ánh. They hid in the forest to avoid the pursuit of Tay Son army. Together, they escaped to the island of Pulo Panjang in the Gulf of Siam. Pigneau hoped that by playing a substantial role in a Nguyễn Ánh victory, he would be in position to lever important concessions for the Catholic Church in Vietnam, helping its expansion in Southeast Asia.

In late 1777, the main part of the Tây Sơn army left Saigon to go north and attack the Trịnh lords, who ruled the other half of Vietnam. Nguyễn Ánh stealthily returned to the mainland, rejoining his supporters and reclaimed the city of Saigon. He was crucially aided by the efforts of Do Thanh Nhon, a senior Nguyễn Lord commander who had organized an army for him, which was supplemented by Cambodian mercenaries and Chinese pirates. The following year, Nhon expelled additional Tây Sơn troops from the surrounding province of Gia Dinh and inflicted heavy losses on the Tây Sơn naval fleet. Taking advantage of the more favorable situation, Nguyễn Ánh sent a diplomatic mission to Siam to propose a treaty of friendship. This potential pact, however, was derailed in 1779 when the Cambodians rose up against their pro-Siamese leader Ang Non II. Nguyễn Ánh sent Nhon to assist the revolt, which eventually saw Ang Non II defeated decisively and executed.

Nhon returned to Saigon with high honor and concentrated his efforts on improving the Nguyễn navy. In 1780, in an attempt to strengthen his political status, Nguyễn Ánh proclaimed himself Nguyễn vương (Nguyễn king or Nguyễn ruler in Vietnamese) with the support of Nhon's Dông Sơn Army. In 1781, Nguyễn Ánh sent further forces to prop up the Cambodian regime against Siamese armies who wanted to reassert their control. Shortly thereafter, Nguyễn Ánh had Nhon brutally murdered. The reason remains unclear, but it was postulated that he did so because Nhon's fame and military success was overshadowing him. At the time, Nhon had much, if not dominant power, behind the scenes. According to later Nguyễn Dynasty chronicles, Nhon's powers included that of deciding who would receive the death penalty, and allocating budget expenditures. Nhon also refused to allocate money for royal spending. Nhon and his men were also reported to have acted in an abrasive and disrespectful manner to Nguyễn Ánh.

The Tây Sơn brothers reportedly broke out in celebration upon hearing of Nhon's execution, as Nhon was the Nguyễn officer that they feared the most. Large parts of Nhon's supporters rebelled, weakening the Nguyễn army, and within a few months, the Tây Sơn had recaptured Saigon mainly on the back of naval barrages. Nguyễn Ánh was forced to flee to Ha Tien, and then onto the island of Phu Quoc. Meanwhile, some of his forces continued to resist in his absence. While the murder of Nhon weakened Nguyễn Ánh in the short term, as many southerners who were personally loyal to Nhon broke away and counter-attacked, it also allowed Nguyễn Ánh to gain autonomy and then take steps towards exerted direct control over the remaining local forces of the Dong Son who were willing to work with him. Nguyễn Ánh also benefited from the support of Chau Van Tiep, who had a power base in the central highlands between the strongholds of the Nguyễn and the Tây Sơn.

In October 1782, the tide shifted again, when forces led by Nguyễn Phúc Mân, Nguyễn Ánh's younger brother, and Chau Van Tiep drove the Tây Sơn out of Saigon. Nguyễn Ánh returned to Saigon, as did Pigneau The hold was tenuous, and a counterattack by the Tây Sơn in early 1783 saw a heavy defeat to the Nguyễn, with Nguyen Man killed in battle. Nguyễn Ánh again fled to Phu Quoc, but this time his hiding place was discovered. He managed to escape the pursuing Tây Sơn fleet to Koh-rong island in the Bay of Kompongsom. Again, his hideout was discovered and encircled by the rebel fleet. However, a typhoon hit the area, and he managed to break the naval siege and escape to another island amid the confusion. In early-1784, Nguyễn Ánh went to seek Siamese aid, which was forthcoming, but the extra 20,000 men failed to weaken the Tây Sơn's hold on power. This forced Nguyễn Ánh to become a refugee in Siam in 1785. To make matters worse, the Tây Sơn regularly raided the rice-growing areas of the south during the harvesting season, depriving the Nguyễn of their food supply. Nguyễn Ánh eventually came to the conclusion that using Siamese military aid would generate a backlash amongst the populace, due to prevailing Vietnamese hostility towards Siam.

Pigneau and French assistance

Deflated by his situation, Nguyễn Ánh asked Pigneau to appeal for French aid, and allowed Pigneau to take his son Nguyễn Phúc Cảnh with him as a sign of good faith. This came about after Nguyễn Ánh had considered enlisting English, Dutch, Portuguese and Spanish assistance. Pigneau advised against Nguyễn Ánh's original plan to seek Dutch aid from Batavia, fearing that the support of the Protestant Dutch would hinder the advancement of Catholicism. Pigneau left Vietnam in December, arriving in Pondicherry, India in February 1785 with Nguyễn Ánh's royal seal. Nguyễn Ánh had authorized him to make concessions to France in return for military assistance. The French administration in Pondicherry, led by acting governor Coutenceau des Algrains, was conservative in outlook and resolutely opposed intervention in southern Vietnam. To compound the already complex situation, Pigneau was denounced by Spanish Franciscans in the Vatican, and he sought to transfer his political mandate to Portuguese forces. The Portuguese had earlier offered Nguyễn Ánh 56 ships to use against the Tây Sơn.

In July 1786, after more than 12 months of fruitless lobbying in Pondicherry, Governor de Cossigny allowed Pigneau to travel back to France to directly ask the royal court for assistance. Arriving at the court of Louis XVI in Versailles in February 1787, Pigneau had difficulty in gathering support for a French expedition in support of Nguyễn Ánh. This was due to the parlous financial state of the country prior to the French Revolution. Pigneau was helped by Pierre Poivre, who had previously been involved in seeking French commercial interests in Vietnam. Pigneau told the court that if France invested in Nguyễn Ánh and acquired a few fortified positions on the Vietnamese coast in return, then they would have the capability to "dominate the seas of China and of the archipelago", and with it, control of Asian commerce. In November 1787, a treaty of alliance was concluded between France and Cochinchina, the European term for southern Vietnam, in Nguyễn Ánh's name. Pigneau signed the treaty as the "Royal Commissioner of France for Cochinchina". France promised four frigates, 1,650 fully equipped French soldiers and 250 Indian sepoys in return for the cession of Pulo Condore and Tourane (Da Nang), as well as tree trade to the exclusion of all other countries. However, the freedom to spread Christianity was not included. However, Pigneau found that Governor Thomas Conway of Pondicherry was unwilling to fulfill the agreement; Conway had been instructed by Paris to determine when to organize the aid, if at all. Pigneau was thus forced to use funds raised in France to enlist French volunteers and mercenaries. He also managed to procure several shipments of arms and munitions from Mauritius and Pondicherry.

Meanwhile, the Royal Court of Siam in Bangkok, under King Rama I, warmly welcomed Nguyễn Ánh. The Vietnamese refugees were allowed to built a small village between Samsen and Bangpho, and named it Long-kỳ (Thai: Lat Tonpho). Ánh had stayed in Siam with a contingent of troops until August 1787. His soldiers served in Siam's war against Bodawpaya of Burma (1785–86). On 18 December 1786, Nguyễn Ánh signed a treaty of alliance with the Portuguese in Bangkok. In the next year, António (An Tôn Lỗi), a Portuguese from Goa, came to Bangkok, brought Western soldiers and warships to Ánh. This disgusted the Siamese and Ánh had to refuse the aid from Portuguese. After this incident, Ánh was no longer trusted by the Siamese.

Having consolidated their hold on southern Vietnam, the Tây Sơn decided to move north to unify the country. However, the withdrawal of troops from the Gia Dinh garrison weakened them their hold on the south. This was compounded by reports that Nguyễn Nhạc was being attacked near Qui Nhơn by his own brother Nguyễn Huệ, and that more Tây Sơn troops were being evacuated from Gia Dinh by their commander Dang Van Tran in order to aid Nguyễn Nhạc. Sensing Tây Sơn vulnerability in the south, Nguyễn Ánh assembled his forces at home and abroad in preparation for an immediate offensive.

Ánh secretly left Siam in the night, leaving a letter in his house, he decided to head for southern Vietnam by boat. As the Vietnamese refugees were preparing to leave, people nearby heard about it and reported it to Phraya Phrakhlang. Phraya Phrakhlang reported it to King Rama I and the Front Palace Maha Sura Singhanat. Sura Singhanat was extremely angry, he chased them personally. At dawn, Sura Singhanat saw Ánh's boat at the mouth of the bay. Finally, the Vietnamese escaped successfully. Ánh arrived at Hà Tiên then to Long Xuyên (Cà Mau), but he failed in his first attempt to recapture Gia Dinh, having failed to convince the local warlord in the Mekong Delta, Vo Tanh to join his assault. The following year, Nguyễn Ánh finally managed to persuade the warlord to join him but after having given his sister to the warlord as a concubine. He eventually succeeded in taking Mỹ Tho, made it the main staging point for his operations, and rebuilt his army. After a hard-fought battle, his soldiers captured Saigon on 7 September 1788. Eventually, Pigneau assembled four vessels to sail to Vietnam from Pondicherry, arriving in Saigon on 24 July 1789. The combined forces helped to consolidate Nguyễn Ánh's hold on southern Vietnam. The exact magnitude of foreign aid and the importance of their contribution to Gia Long's success is a point of dispute. Earlier scholars asserted that up to 400 Frenchmen enlisted, but more recent work has claimed that less than 100 soldiers were present, along with approximately a dozen officers.

Consolidation of southern Vietnam

After more than a decade of conflict, Nguyễn Ánh had finally managed to gain control of Saigon for long enough to have time to start a permanent base in the area and prepare to build up for a decisive power struggle with the Tây Sơn. The area around Saigon, known as Gia Dinh, began to be referred to as its own region, because Nguyễn Ánh's presence was becoming entrenched, distinguishing and associating the area with a political base. Nguyễn Ánh's military was able to consolidate, and a civil service was reestablished. According to the historian Keith Taylor, this was the first time that the southern third of Vietnam was integrated "as a region capable of participating successfully in war and politics among Vietnamese speakers", which could "compete for ascendancy with all the other places inhabited by speakers of the Vietnamese language". A Council of High Officials consisting of military and civil officials was created in 1788, as was a tax collection system. In the same year, regulations were passed to force half the male population of Gia Dinh to serve as conscripts, and two years later, a system of military colonies was implemented to bolster the Nguyễn support base across all racial groups, including ethnic Khmers and Chinese.

The French officers enlisted by Pigneau helped to train Nguyễn Ánh's armed forces and introduced Western technological expertise to the war effort. The navy was trained by Jean-Marie Dayot, who supervised the construction of bronze-plated naval vessels. Olivier de Puymanel was responsible for training the army and the construction of fortifications. He introduced European infantry training, formations and tactics while also facilitating various methods of manufacturing and using European-style artillery, thereby making cannonry and projectiles a central part of the military. Pigneau and other missionaries acted as business agents for Nguyễn Ánh, purchasing munitions and other military matériel. Pigneau also served as an advisor and de facto foreign minister until his death in 1799. Upon Pigneau's death, Gia Long's funeral oration described the Frenchman as "the most illustrious foreigner ever to appear at the court of Cochinchina". Pigneau was buried in the presence of the crown prince, all mandarins of the court, the royal bodyguard of 12,000 men and 40,000 mourners.

Fortifications

Layout of the original citadel.

Following the recapture of Saigon, Nguyễn Ánh consolidated his power base and prepared the destruction of the Tây Sơn. His enemies had regularly raided the south and looted the annual rice harvests, so Nguyễn Ánh was keen to strengthen his defence. One of Nguyễn Ánh's first actions was to ask the French officers to design and supervise the construction of a modern European-style citadel in Saigon. The citadel was designed by Theodore Lebrun and de Puymanel, with 30,000 people mobilized for its construction in 1790. The townsfolk and the mandarins were punitively taxed for the work and the laborers were so over-worked that they revolted. When finished, the stone citadel had a perimeter measuring 4,176 meters in a Vauban model. The fortress was bordered on three sides by pre-existing waterways, bolstering its natural defensive capability. Following the construction of the citadel, the Tây Sơn never again attempted to sail down the Saigon River and try to recapture the city, its presence having endowed Nguyễn Ánh with a substantial psychological advantage over his opponents. Nguyễn Ánh took a keen personal interest in fortifications, ordering his French advisors to travel home and bring back books with the latest scientific and technical studies on the subject. The Nguyễn royal palace was built inside the citadel.

Agricultural reform and economic growth

With the southern region secured, Nguyễn Ánh turned his attention to agricultural reforms. Due to Tây Sơn naval raids on the rice crop via inland waterways, the area suffered chronic rice shortages. Although the land was extremely fertile, the region was agriculturally underexploited, having been occupied by Vietnamese settlers only relatively recently. Furthermore, agricultural activities had also been significantly curtailed during the extended warfare with the Tây Sơn. Nguyễn Ánh's agricultural reforms were based around extending to the south a traditional form of agrarian expansion, the đồn điền, which roughly translates as "military settlement" or "military holding", the emphasis being on the military origin of this form of colonization. These were first used during the 15th-century reign of Lê Thánh Tông in the southward expansion of Vietnam. The central government supplied military units with agricultural tools and grain for nourishment and planting. The soldiers were then assigned land to defend, clear and cultivate, and had to pay some of their harvest as tax. In the past, a military presence was required because the land had been seized from the conquered indigenous population. Under Nguyễn Ánh's rule, pacification was not usually needed but the basic model remained intact. Settlers were granted fallow land, given agricultural equipment, work animals, and grain. After several years, they were required to pay grain tax. The program greatly reduced the amount of idle, uncultivated land. Large surpluses of grain, taxable by the state, soon resulted.

By 1800, the increased agricultural productivity had allowed Nguyễn Ánh to support a sizeable army of more than 30,000 soldiers and a navy of more than 1,200 vessels. The surplus from the state granary was sold to European and Asian traders to facilitate the importation of raw materials for military purposes, in particular iron, bronze, and sulfur. The government also purchased caster sugar from local farmers and traded it for weapons from European manufacturers. The food surplus allowed Nguyễn Ánh to engage in welfare initiatives that improved morale and loyalty among his subjects, thereby increasing his support base. The surplus grain was deposited in granaries built along the northward route out of Saigon, following the advance of the Nguyễn army into Tây Sơn territory. This allowed his troops to be fed from southern supplies, rather than eating from the areas that he was attempting to conquer or win over. Newly acquired regions were given tax exemptions, and surrendered Tây Sơn mandarins were appointed to equivalent positions with the same salaries in the Nguyễn administration.

Naval buildup

Nguyễn Ánh used his new Chu Su Naval workshop to improve his inferior navy, which was much smaller than the Tây Sơn fleet and hitherto unable to prevent their rice raids. Nguyễn Ánh had first attempted to acquire modern naval vessels in 1781, when on the advice of Pigneau, he had chartered Portuguese vessels of European design, complete with crew and artillery. This initial experience proved to be disastrous. For reasons that remain unclear, two of the vessels fled in the midst of battle against the Tây Sơn, while angry Vietnamese soldiers killed the third crew. In 1789, Pigneau returned to Vietnam from Pondicherry with two vessels, which stayed in the Nguyễn service long-term. Over time, Vietnamese sailors replaced the original French and Indian crew under the command of French officers. These vessels became the foundation for an expanded military and merchant Nguyen naval force, with Nguyễn Ánh chartering and purchasing more European vessels to reinforce Vietnamese-built ships. However, traditional Vietnamese-style galleys and small sailing ships remained the mainstay of the fleet. By 1794, two European vessels were operating together with 200 Vietnamese boats against the Tây Sơn near Qui Nhơn. In 1799, a British trader by the name of Berry reported that the Nguyễn fleet had departed Saigon along the Saigon River with 100 galleys, 40 junks, 200 smaller boats, and 800 carriers, accompanied by three European sloops. In 1801, one naval division was reported to have included nine European vessels armed with 60 guns, five vessels with 50 guns, 40 with 16 guns, 100 junks, 119 galleys, and 365 smaller boats.

Most of the European-style vessels were built in the shipyard that Nguyễn Ánh had commissioned in Saigon. He took a deep personal interest in the naval program, directly supervising the work and spending several hours a day at the dockside. One witness noted "One principal tendency of his ambition is to naval science, as a proof of this he has been heard to say he would build ships of the line on the European plan." By 1792, fifteen frigates were under construction, with a design that mixed Chinese and European specifications, equipped with 14 guns. The Vietnamese learned European naval architecture by dismantling an old European vessel into its components, so that Vietnamese shipbuilders could understand the separate facets of European shipbuilding, before reassembling it. They then applied their newfound knowledge to create replicas of the boats. Nguyễn Ánh studied naval carpentry techniques and was said to be adept at it, and learned navigational theory from the French books that Pigneau translated, particularly Denis Diderot and Jean le Rond d'Alembert's Encyclopédie. The Saigon shipyard was widely praised by European travelers.

Despite his extensive reliance on French officers in matters of military technology, Nguyễn Ánh limited his inner military circle to loyal Vietnamese. The Frenchmen decried his refusal to take their tactical advice. Chaigneau reported that the Europeans continually urged Nguyễn Ánh to take the initiative and launch bold attacks against Tây Sơn installations. Nguyễn Ánh refused, preferring to proceed slowly, consolidating his gains in one area and strengthening his economic and military base, before attacking another. In the first four years after establishing himself in Saigon in 1788, Nguyễn Ánh focused on tightening his grip on the Gia Dinh area and its productive rice paddies, and although his forces exerted a degree on control over areas to the north such as Khanh Hoa, Phu Yen and Binh Thuan, their main presence in the northern areas were mainly through naval forces and not concentrated on land occupation. This was because those areas were not very fertile in terms of rice production and were often affected by famines, and occupying the land would have meant an obligation to feed the populace, putting a strain on resources. During this four-year period, Nguyễn Ánh sent missions to Siam, Cambodia and south to the Straits of Malacca and purchased more European military equipment.

Over time, Nguyễn Ánh gradually reduced the military role of his French allies on the battlefield. In the naval battle at Thi Nai in 1792, Dayot led the Nguyễn naval attack, but by 1801, a seaborne offensive in the same area was led by the Nguyen Van Truong, Vo Duy Nguy and Lê Văn Duyệt, with Chaigneau, Vannier, and de Forsans in supporting positions. The infantry attack on Qui Nhơn in 1793 was conducted, according to Nguyen historiography, in cooperation with "Western soldiers". The same source recorded that by 1801, Nguyen operations in the same area were directed by Vietnamese generals, whereas Chaigneau and Vannier were responsible for organizing supply lines.

Unification of Vietnam

Vietnamese "Tirailleur" soldiers of the Nguyễn dynasty

In 1792, the middle and the most notable of the three Tây Sơn brothers, Nguyễn Huệ Quang Trung, who had gained recognition as Emperor of Vietnam by driving the Lê dynasty and China out of northern Vietnam, died suddenly. Nguyễn Ánh took advantage of the situation and attacked northwards. By now, the majority of the original French soldiers, whose number peaked at less than 80 by some estimates, had departed. The majority of the fighting occurred in and around the coastal towns of Nha Trang in central Vietnam and Qui Nhơn further to the north in Bình Định Province, the birthplace and stronghold of the Tây Sơn.

Nguyễn Ánh began by deploying his expanded and modernized naval fleet in raids against coastal Tây Sơn territory. His fleet left Saigon and sailed northward on an annual basis during June and July, carried by southwesterly winds. The naval offensives were reinforced by infantry campaigns. His fleet would then return south when the monsoon ended, on the back of northeasterly winds. The large European wind-powered vessels gave the Nguyễn navy a commanding artillery advantage, as they had a superior range to the Tây Sơn cannons on the coast. Combined with traditional galleys and a crew that was highly regarded for its discipline, skill and bravery, the European-style vessels in the Nguyễn fleet inflicted hundreds of losses against the Tây Sơn in 1792 and 1793.

In 1794, after a successful campaign in the Nha Trang region, Nguyễn Ánh ordered de Puymanel to build a citadel at Duyen Khanh, near the city, instead of retreating south with the seasonal northeasterly breeze. A Nguyen garrison was established there under the command of Nguyễn Ánh's eldest son and heir, Nguyễn Phúc Cảnh, assisted by Pigneau and de Puymanel. The Tây Sơn laid siege to Duyen Khanh in May 1794, but Nguyen forces were able to keep them out. Shortly after the siege ended, reinforcements arrived from Saigon and offensive operations against the Tây Sơn duly resumed. The campaign was the first time that the Nguyễn were able to operate in Tây Sơn heartland during an unfavorable season. The defensive success of the citadel was a powerful psychological victory for the Nguyễn, demonstrating their ability to penetrate Tây Sơn territory at any time of the year. The Nguyễn then proceeded to slowly erode the Tây Sơn heartland.

Heavy fighting occurred at the fortress of Qui Nhơn until it was captured in 1799 by Nguyen Canh's forces. However, the city was quickly lost and was not regained until 1801. The superior firepower of the improved navy played the decisive role in the ultimate recapture of the city, supporting a large overland attack. With the capture of their stronghold at Qui Nhơn, the vanquishing of the Tây Sơn was inevitable. In June, the central city of Huế, the former capital of the Nguyễn, fell and Nguyễn Ánh crowned himself emperor, under the reign name Gia Long, which was derived from Gia Định (Saigon) and

Thăng Long (Hanoi) to symbolize the unification of northern and southern Vietnam. He then quickly overran the north, with Hanoi captured on 22 July 1802. After a quarter-century of continuous fighting, Gia Long had unified these formerly fractious territorie, ultimately leading what is now modern Vietnam and elevated his family to a position never previously occupied by any Vietnamese royalty. Vietnam had never before occupied a larger landmass. Gia Long became the first Vietnamese ruler to reign over territory stretching from China in the north, all the way to the Gulf of Siam and the Cà Mau peninsula in the south. Gia Long's then petitioned the Qing dynasty of China for official recognition, which was promptly granted. The French failure to honor the treaty signed by Pigneau meant Vietnam was not bound to cede the territory and trading rights that they had promised.

Due to a Tây Sơn massacre of ethnic Chinese, the Nguyễn were subsequently supported by most ethnic Chinese against the Tây Sơn. The Tây Sơn's downfall and defeat at the hands of Nguyễn Phúc Ánh was therefore due, at least in part, to the ethnic Chinese support given the Nguyễn.

Rule

Gia Long's rule was noted for its strict Confucian orthodoxy. Upon toppling the Tây Sơn, he repealed their reforms and reimposed classical Confucian education and civil service systems. He moved the capital from Hanoi in the north to Huế in central Vietnam to reflect the southward migration of the population over the preceding centuries. The Emperor built new fortresses and a palace in his new capital. Using French expertise, Gia Long modernized Vietnam's defensive capabilities and, in recognition of the assistance of his French friends, he permitted the activities of Catholic missionaries, something, however, which was less tolerated by his successors. Under Gia Long's rule, Vietnam strengthened its military dominance in Indochina, expelling Siam from Cambodia and turning it into a vassal state. Despite this, he was relatively isolationist in outlook towards European powers.

Renaming Vietnam

Gia Long decided to join the Imperial Chinese Tributary System. He sent an embassy to Qing China, and requested to change his country's name to Nam Việt (南越). Gia Long explained that the word Nam Việt derived from An Nam (安南) and Việt Thường (越裳), two toponyms mentioned in ancient Chinese records where located in northern and southern Vietnam respectively, to symbolize the unification of the country. The Qing Jiaqing Emperor of China refused his request because it had an identical name with the ancient kingdom Nam Việt (Nanyue), and the territory of Nam Việt contained Liangguang which belonged to Qing China at that time. Instead, Jiaqing agreed to change it to Việt Nam (越南). Gia Long's Đại Nam thực lục contains the diplomatic correspondence over the naming.

However, Gia Long copied the Imperial Chinese system, based on the Chinese Confucian model and attempting to create a Vietnamese Imperial tributary system. "Trung Quốc" (中國) was used as a name for Vietnam by Gia Long in 1805.

It was said "Hán di hữu hạn" (漢夷有限, "the Vietnamese and the barbarians must have clear borders") by the Gia Long Emperor (Nguyễn Phúc Ánh) when differentiating between Khmer and Vietnamese. Minh Mạng implemented an acculturation integration policy directed at minority non-Vietnamese peoples. Thanh nhân (清人) was used to refer to ethnic Chinese by the Vietnamese while Vietnamese called themselves as Hán nhân (漢人) in Vietnam during the 1800s under Nguyễn rule.

Administrative structure

During the war era, Nguyễn Ánh had maintained an embryonic bureaucracy in an attempt to prove his leadership ability to the people. Due to the incessant warfare, military officers were generally the most prominent members of his inner circle. This dependency on military backing continued to manifest itself throughout his reign. Vietnam was divided into three administrative regions. The old patrimony of the Nguyễn formed the central part of the empire (vùng Kinh Kỳ), with nine provinces, five of which were directly ruled by Gia Long and his mandarins from Huế.

The central administration at Huế was divided into six ministries: Public affairs, finance, rites, war, justice, and public works. Each was under a minister, assisted by two deputies and two or three councilors. Each of these ministries had around 70 employees assigned to various units. The heads of these ministries formed the Supreme Council. A treasurer-general and a Chief of the Judicial Service assisted a governor-general, who was in charge of a number of provinces. The provinces were classified into trấn and dinh. These were in turn divided into phủ, huyện and châu. All important matters were examined by the Supreme Council in the presence of Gia Long. The officials tabled their reports for discussion and decision-making. The bureaucrats involved in the Supreme Council were selected from the high-ranking mandarins of the six ministries and the academies.

Gia Long handled the northern and southern regions of Vietnam cautiously, not wanting them to be jarred by rapid centralization after centuries of national division. Tonkin, with the administrative seat of its imperial military protector (quan tổng trấn) at Hanoi, had thirteen provinces (tổng trấn Bắc Thành), and in the Red River Delta, the old officials of the Le administration continued in office. In the south, Saigon was the capital of the four provinces of Cochinchina (tổng trấn Nam Hà), as well as the seat of the military protector. The citadels in the respective cities directly administered their military defense zones. This system allowed Gia Long to reward his leading supporters with highly powerful positions, giving them almost total autonomy in ordinary administrative and legal matters. This system persisted until 1831–32, when his son Minh Mạng centralized the national government.

In his attempts to re-establish a stable administration after centuries of civil war, Gia Long was not regarded as being innovative, preferring the traditional administration framework. When Gia Long unified the country, it was described by Charles Maybon as being chaotic: "The wheels of administration were warped or no longer existed; the cadres of officials were empty, the hierarchy destroyed; taxes were not being collected, lists of communal property had disappeared, proprietary titles were lost, fields abandoned; roads bridges and public granaries had not been maintained; work in the mines had ceased. The administration of justice had been interrupted, every province was a prey to pirates, and violation of law went unpunished, while even the law itself had become uncertain."

Foreign military relations

During the 17th and 18th centuries, the Cambodian empire had been in decline and Vietnamese people migrated south into the Mekong Delta, which had previously been Khmer territory. Furthermore, Cambodia had been periodically invaded by both Vietnam and Siam. Cambodia lurched uneasily between both poles of domination as dictated by the internal strife of her two larger neighbors. In 1796, Ang Eng, a pro-Siamese king had died, leaving Ang Chan, who was born in 1791. When Gia Long unified Vietnam, Eng was given investiture by Siam in order to hold out Vietnamese influence, but in 1803, a Cambodian mission paid tribute to Vietnam in attempt to placate Gia Long, something that became an annual routine. In 1807, Ang Chan requested formal investiture as a vassal of Gia Long. Gia Long responded by sending an ambassador bearing the book of investiture, together with a seal of gilded silver. In 1812, Ang Chan refused a request from his brother Ang Snguon to share power, leading to a rebellion. Siam sent troops to support the rebel prince, hoping to enthrone him and wrest influence from Gia Long over Cambodia. In 1813, Gia Long responded by sending a large military contingent that forced the Siamese and Ang Snguon out of Cambodia. As a result, a Vietnamese garrison was permanently installed in the citadel at Phnom Penh, the Cambodian capital. Thereafter, Siam made no attempts to regain control of Cambodia during Gia Long's rule.

Napoleon's aims to conquer Vietnam as a base to threaten British possessions in India never materialized, having been preoccupied by vast military ambitions on mainland Europe. However, France remained the only European power with permanent spokesmen in Vietnam during his reign.

Trade relations

Pigneau's aborted deal with France allowed Gia Long to keep his country closed to western trade. Gia Long was generally dismissive of European commercial overtures. This was part of a policy of trying to maintain friendly relations with every European power by granting favors to none. In 1804, a British delegation attempted to negotiate trading privileges with Vietnam. It was the only offer of its kind until 1822, such was the extent of European disinterest in Asia during the Napoleonic Wars. Gia Long had purchased arms from British firms in Madras and Calcutta on credit, prompting the British East India Company to send John Roberts to Huế. However, Roberts's gifts were turned away and the negotiations for a commercial deal never started. The British then made a request for the exclusive right to trade with Vietnam and the cession of the island of Cham near Faifo, which was rejected, as were further approaches from the Netherlands. Both of these failed attempts were attributed to the influence of the French mandarins. In 1817, the French Prime Minister Armand-Emmanuel du Plessis dispatched the Cybele, a frigate with 52 guns to Tourane (now Da Nang) to "show French sympathy and to assure Gia Long of the benevolence of the King of France". The captain of the vessel was turned away, ostensibly on grounds of protocol for not carrying a royal letter from the French king.

Gia Long kept four French officers in his service after his coronation: Philippe Vannier, Jean-Baptiste Chaigneau, de Forsans and the doctor Despiau. All became high ranking mandarins and were treated well. They were given 50 bodyguards each, ornate residences and were exempt for having to prostrate before the emperor. Recommendations from French officials in Pondicherry to Napoleon Bonaparte suggesting the re-establishment of diplomatic relations with Vietnam were fruitless due to the preoccupation with war in Europe. However, French merchants from Bordeaux were later able to begin trading with Vietnam after the further efforts of the Duc de Richelieu.

Domestic policies and capital works

Gia Long abolished all large landholding by princes, nobles, and high officials. He dismantled the 800-year-old practice of paying officials and rewarding or endowing nobles with a portion of the taxes from a village or a group thereof. Existing highways were repaired and new ones constructed, with the north-south road from Saigon to Lạng Sơn put under restoration. He organized a postal service to operate along the highways and public storehouses were built to alleviate starvation in drought-affected years. Gia Long enacted monetary reform and implemented a more socialized agrarian policy. However, the population growth far outstripped that of land clearing and cultivation. There was little emphasis on innovation in agricultural technology, so the improvements in productivity were mainly derived from increasing the amount of cultivated farmland.

Although the civil war was over, Gia Long decided to add to the two citadels that had been built under the supervision of French officers. Gia Long was convinced of their effectiveness and during his 18-year reign, a further 11 citadels were built throughout the country. The majority were built in the Vauban style, with pentagonal or hexagonal geometry, while a minority, including the one in Huế, were built in a four-sided traditional Chinese design. The fortresses were built at Vinh, Thanh Hóa, Bắc Ninh, Hà Tĩnh, Thái Nguyên and Hải Dương in the north, Huế, Quảng Ngãi, Khánh Hòa and Bình Định in the centre, and Vĩnh Long in the Mekong Delta. Construction was at its most intense in the early phase of Gia Long's reign, only one of the 11 was built in the last six years of his rule. De Puymanel and Lebrun left Vietnam before the end of the war, so the forts were designed by Vietnamese engineers who oversaw the construction. The position of Citadel Supervision Officer was created under the Ministry of War and made responsible for the work, underlining the importance that Gia Long placed on fortifications. Gia Long's fortifications program was marred by accusations that the people labored all day and part of the night in all weather conditions, and that as a direct consequence, land went fallow. Complaints of mandarin corruption and oppressive taxation were often leveled at his government. Following his coronation, Gia Long drastically reduced his naval fleet, and by the 1810s, only two of the European-style vessels were still in service. The downsizing of the navy was mainly attributed to budgetary constraints caused by heavy spending on fortifications and transport infrastructures such as roads, dykes, and canals. However, in 1819, a new phase of shipbuilding was launched, with Gia Long personally supervising the dockyards.

Social policy

In order to train and recruit government officials, Gia Long revived the Confucian court examinations that had been abolished by the Tây Sơn. In 1803, he founded the National Academy (Quốc Tử Giám) at Huế. Its objective was to educate the sons of mandarins and meritorious students in Confucian classical literature. In 1804, Gia Long promulgated edicts establishing similar schools in the provinces, as well as guidelines to regulate their staff and curriculum. He appointed Directors of Education (quan đốc học) to oversee the provincial education system and the selection process for the entrance examinations to the National Academy, beginning in 1802. The Directors were assisted by Subordinate and Assistant Directors (phó đốc học or trợ-giáo). Gia Long explained to his court in 1814 that the goal was to create a cadre of classically educated, politically loyal administrators:

In 1807, Gia Long opened the first civil service examinations held under the Nguyễn dynasty, staged at regional level. From then on, the training and selection process for the imperial bureaucracy was largely centered on examinations. The curriculum for the examinations consisted of the Four Books and Five Classics, which focused on Chinese history leading up to the Song dynasty, while regarding other knowledge as irrelevant.

Gia Long promulgated a new legal code to replace the system that had existed since the Hong Duc era of Lê Thánh Tông in the 15th century. Work started in 1811 under a group of scholars led by Nguyễn Văn Thành, and in 1815, the Bộ luật Gia Long (Gia Long Code) was issued. Although Gia Long claimed that his new system was a mixture of the Le code and Qing dynasty system of China, most scholars regard it as being a near-complete copy of the Qing code. The code was later translated into French by Paul-Louis-Félix Philastre. It focused on strengthening the power and authority of the emperor, his mandarins, and the traditional family unit. In cases of serious crimes, particularly those against the state, collective punishment was meted out to the family of the convict, including the death penalty.

Now that Vietnam was unified, the center of gravity of the country moved further south, following centuries of southerly migration and conquest, so Gia Long moved the seat of government from Hanoi to Huế. Gia Long rebuilt the old citadel of Phú Xuân into a fortress stronghold. The structure was a square shape of 2.5 km per side. A 9 m rampart was encased with masonry and protected by protruding bastions, each defended by 36 guns. The exterior and interior were flanked and reinforced by a series of moats. The citadel's defenders included an 800-strong elephant troop. The new palace structure, protocol and court dress were all taken directly from Qing dynasty styles, and his palace and fortress was intended to be a smaller copy of the Chinese Forbidden City in the 1800s.

Gia Long tolerated the Catholic faith of his French allies and permitted unimpeded missionary activities out of respect to his benefactors. The missionary activity was dominated by the Spanish in Tonkin and French in the central and southern regions. At the time of his death, there were six European bishops in Vietnam. The population of Christians was estimated at 300,000 in Tonkin and 60,000 in Cochinchina. However, he expressed dismay at the Catholic condemnation of the traditional ancestor worship, a basic tenet of Vietnamese culture. Gia Long was also known for his disdain for Buddhism, the religion practiced by the majority of the population. Despite its popularity among ladies of the court, Gia Long often restricted the activities of Buddhists.

In August 1802, Gia Long retaliated against the captured Tây Sơn leadership who had executed his family in the 1770s. The surviving members of the family and its leading generals and their families were executed. The remains of Quang Trung and his queen were exhumed and desecrated, and his son, the last Tây Sơn monarch Quang Toản was bound to four elephants and torn apart. Gia Long repealed the changes enacted by Quang Trung and reverted to the prior Confucian orthodoxy. This included restoring the civil service to the forefront of decision making, ahead of the army, and reversed Quang Trung's education reforms, which put science before the study of Confucian literature.

Family and succession

Minh Mạng, Gia Long's fourth son and successor.

Gia Long had many wives, but the most famous consorts are Empress Thừa Thiên, Empress Thuận Thiên, and Consort Lê Ngọc Bình.

In 1780, during the war against the Tây Sơn, he married Tống Thị Lan, the daughter of a Nguyen general. She bore him two sons, the first being Nguyễn Phúc Chiêu, who died shortly after birth in Phú Quốc island, and later Crown Prince Nguyễn Phúc Cảnh. Following Gia Long's ascension to the throne, she became Empress consort and was given the title of Empress Thừa Thiên posthumously. Around 1781, during the war with the Tây Sơn, he married his second wife Trần Thị Đang, a daughter of one of his ministers. She bore him three sons, Nguyễn Phúc Đảm, Nguyen Phuc Dai and Nguyen Phuc Chan, and was posthumously given the title of Empress Thuận Thiên. After his conquest of Vietnam, Gia Long, took his third wife, Lê Ngọc Bình. A daughter of Lê Hiển Tông, the second-last emperor of the Lê dynasty, she was betrothed by Emperor Quang Trung to his son Quang Toản. After Gia Long defeated the Tây Sơn and executed Quang Toan, he took her as his wife. Gia Long had almost 100 concubines who were daughters of his mandarins; Gia Long did not favor polygamy but he did so to secure the loyalty of his inner circle.

As Crown Prince Nguyen Canh had died of smallpox during the war against the Tây Sơn, it was assumed that Canh's son would succeed Gia Long as emperor, but in 1816 Nguyễn Phúc Đảm, the son of his second wife, was appointed instead, and ruled as Minh Mạng. Gia Long chose him for his strong character and his deep aversion to westerners, whereas Canh's lineage had converted to Catholicism and were reluctant to maintain their Confucian traditions such as ancestor worship. Before his accession, Nguyễn Phúc Đảm was reported to have praised the Japanese for having expelled and eradicated Christianity from their country. Gia Long told his son to treat the Europeans respectfully, especially the French, but not to grant them any position of preponderance. Gia Long died on 3 February 1820 and was buried at the Thien Tho Tomb and posthumously named Thế Tổ Cao Hoàng đế.

早年生涯

阮福映原名阮福暖（），又名阮福種（），是阮福㫻與阮氏環的第三子。阮福㫻是阮福濶的次子。據阮朝的官方正史記載，1765年阮福濶逝世，因世子阮福昊已死，便遺命讓阮福㫻繼位。但權臣張福巒卻篡改了遺詔，讓年幼的第十六子阮福淳繼位。不過，也有歷史學家認為阮福㫻被確立為繼承人可能是19世紀阮朝建立以後才出現的一種觀點；阮福昊死後，阮福濶指定阮福淳繼位，阮福昊的長子阮福暘為替補人選。而在後來的西山之亂中，阮福暘的聲望遠遠超過了阮福淳，而此時阮福映在各位王子中只是個不起眼的小人物。

阮福濶逝世時，阮福映年僅四歲，同父親阮福㫻一起被幽禁在宮中，不久父親阮福㫻就死了。阮福淳年少貪玩，專權的張福巒又貪婪殘暴，導致了百姓的不滿。1771年，阮岳、阮侶、阮惠三兄弟發動西山起義，立即得到了南河各地的響應。1774年，北河的鄭主鄭森見南河大亂，派黃五福南下討伐。阮福映隨定王阮福淳南逃至嘉定（今胡志明市一帶）。此時，阮福映被定王授予掌使的官職，統帥左翊軍。阮朝史料稱，他雖然年少，但多出奇謀，深得諸將的尊敬，也得到了定王的器重。

1777年，西山朝君主阮岳派遣阮惠、阮侶攻打嘉定，年僅十五歲的阮福映被太上王阮福淳派往三埠（位於今前江省一帶）募兵。不久，舊阮的新政王阮福暘同眾多宗室大臣一起，在龍湖營（今永隆省一帶）被西山軍俘虜殺害。太上王逃往橙江（位於今前江省一帶），阮福映率東山軍將其迎接到芹苴。隨後，太上王在龍川（今金甌省）被阮惠俘虜並殺害。許多阮氏王子遇害，但阮福映倖免於難。

他逃到了瀝架，被天主教牧師保羅·誼（Paul Nghi，Phaolô Hồ Văn Nghị）藏了起來。此後他逃到了河僊鎮，在那裡，他遇上了法國巴黎外方傳教會的百多祿主教。得到保羅·誼的情報後，百多祿避開了在柬埔寨的西山軍，前來幫助阮福映。阮福映許諾在奪回政權之後將會給予基督教自由傳播的權力，因此百多祿動心了。他們一起進入森林逃避西山軍追捕，此後二人一起逃亡到了土硃嶼。

重回南河

嘉定一帶的爭奪戰

阮惠、阮侶在攻滅舊阮政權之後，留總督凋鎮守嘉定，自己則率軍回到歸仁。在得知西山軍主力撤離嘉定之後，阮福映率其支持者自土硃嶼回到龍川，起兵反抗西山朝。阮文仁、楊公澄將阮福映迎至沙瀝（今同塔省沙瀝市）。舊阮殘餘勢力紛紛舉兵響應，杜清仁、黎文勻、阮文弘、宋福匡、宋福樑等將驅逐了總督凋，奪回了嘉定城。舊阮勢力得以復闢，阮福映被眾將推舉為「大元帥攝國政」，當時年僅十七歲。

阮岳派軍隊前來攻打，被杜清仁率東山軍擊退。阮福映趁機派遣黎文勻發起反攻，奪取了平順、延慶兩府。在內政方面，阮福映重新設置了阮主時代的府僚，並制定稅例抽稅養兵，製造戰船積極備戰。在百多祿的幫助下，舊阮製造了大量新式武器，包括了新式武器手榴彈。百多祿還從葡萄牙購買了三艘西式軍艦，聘請法國探險家幔槐（Manuel）為船長。舊阮勢力再次強大，嘉定城附近的藩安、邊和、定祥、永清、河僊鎮都被舊阮收復，西山軍屢次征討都未能成功。日趨強大的舊阮甚至派遣介入了柬埔寨的內戰。1779年，親暹羅的安農二世（匿螉嫩）登上了柬埔寨王位。阮福映派杜清仁、胡文璘前去征討，殺死安農，擁立親越南的安英（匿螉印）登位，並留胡文璘守柬埔寨。

1780年陰曆正月，阮福映正式稱王，人稱「阮王」（）。阮福映使用後黎朝的景興年號，並恢復使用廣南阮主的「大越國阮主永鎮之寶」。但次年因杜清仁功高震主，阮福映命宋福添殺之；其下屬的東山軍紛紛背叛，舊阮陷入混亂之中。暹羅國王鄭昭得知之後，趁機派遣通鑾·扎克里（即後來的拉瑪一世）、素拉西（即後來的二王素拉辛哈那）二兄弟攻打柬埔寨，阮福映遣阮有瑞前去支援。由於當時鄭昭猜忌通鑾，將通鑾二兄弟的家小監禁；通鑾二人得知後，便與阮有瑞達成和解，相約為兄弟。恰巧此時暹羅發生兵變，通鑾·扎克里率軍回國平亂，尋獲鄭昭誅殺之，並殺死發動政變的披耶·訕。隨後，昭披耶·扎克里繼位為新的暹羅國王——拉瑪一世，以素拉西為第二王，通因為第三王。舊阮因而鞏固了其在柬埔寨的霸權地位。

1782年陰曆三月，阮岳在歸仁得知舊阮內亂，與阮惠親率水步兵三千、戰船若干南下攻打嘉定。舊阮軍與西山軍在嘉定附近的交戰。雖然舊阮軍有三艘軍艦的參戰，但西山軍的水軍趁順風到來之際猛衝舊阮水軍。由於指揮上的失誤，舊阮軍隊大敗，幔槐陣亡，並損失了一艘軍艦。這場戰役中舊阮軍隊遭到毀滅性打擊，阮福映被迫棄嘉定城，逃往富國島。西山軍攻取嘉定，留杜閑蟄守城，阮岳、阮惠率主力部隊回到歸仁。

再失王位，流亡暹羅

阮福映敗逃富國島，但其支持者依然抗擊西山朝。就在阮岳、阮惠班師回朝之後，同年的陰曆十月，富安府的朱文接率軍起兵，阮福映的弟弟阮福旻也舉兵響應。朱文接收復了嘉定，迎阮福映回城。但次年陰曆二月西山朝又派阮惠、阮侶前來攻打。西山軍在四岐江旁背水一戰，舊阮大敗，阮福旻陣亡，重要將領楊公澄、阮黃德被俘。阮福映不得已，再次逃往富國島。這次阮惠希望一舉殲滅阮福映勢力，於是在休整兵馬之後，於六月攻打富國島。阮福映不敵，敗走崑崙島。阮惠再攻崑崙島，由於西山軍許多戰船遭遇風暴而傾覆，阮惠被迫罷兵。阮福映經古骨嶼（今閣骨島）逃回富國島。

身處富國島的阮福映殘部沒有糧草，只能採草芋充飢。當時百多祿正在暹羅的尖竹汶傳教，阮福映派人前去商議，決定派遣範文仁、阮文廉護送嫡長子阮福景，隨百多祿前往法國求救。但因風不順，百多祿一行始終未能出發。另一方面，阮福映派朱文接前往暹羅求救。1783年底，朱文接到達暹羅首都曼谷，覲見了暹羅國王拉瑪一世。拉瑪一世派大將知蚩多率水軍前去接應阮福映。暹羅水軍於次年陰曆二月到達河僊鎮，與阮福映商討共抗西山朝的事宜。阮福映隨暹羅軍隊來到曼谷，在那裡招募逃往到暹羅的舊部，伺機返回越南。拉瑪一世以非常隆重的禮節歡迎阮福映，並答應將出兵助其歸國。

1784年（西山朝泰德七年），阮福映率舊部朱文接、阮文誠、鄚子泩、阮文威等攻打嘉定。暹羅國王拉瑪一世先派六昆、沙苑會同暹羅任命的柬埔寨攝政昭披耶·阿派普貝至柬埔寨，由此進攻嘉定；七月後又派大將昭曾、昭霜率士兵二萬、戰船三百艘，從曼谷出發，渡海攻打嘉定。

暹羅軍勢如劈竹，連破瀝架（今堅江省迪石市）、巴色（今朔莊省朔莊市）、茶溫（今永隆省茶溫縣）、斌沏（在今永隆省）、沙瀝（今同塔省沙瀝市社）等地。黎文勻據茶津（今前江省）響應阮福映。舊阮方面的統帥朱文接在攻打斌沏的時候陣亡，阮福映任命黎文勻接替其統帥之職。西山軍守將張文多不敵，被迫撤離了嘉定，派鄧文真向歸仁求救。阮岳得悉後，便派阮惠前去防禦，駐軍於是美湫。

暹羅軍隊在嘉定一帶燒殺搶劫，掠奪了大量金銀財寶和奴隸送回暹羅。暹羅人對阮福映表現得非常輕慢。阮福映也看到了暹羅出兵相助事實上是想乘機佔領嘉定之地，對此非常失望，認為暹羅必敗，事先派遣鄚子泩來到鎮江（今芹苴市、後江省一帶）組織戰船，為自己留下後路。

阮惠派兵數次攻打暹羅水寨，然後撤退。此後，又遣人贈送給昭曾豐厚的禮物，請求不要幹涉西山朝與舊阮的內戰。昭曾高興地收下了禮物，這使暹羅更加輕敵，也造成了暹羅與舊阮雙方互相猜疑。阮惠便使用誘敵深入之計，在瀝涔、吹蔑（亦作蔑）一帶設伏引誘暹羅、舊阮聯軍到來，大破之。這場戰役發生在1785年的陰曆四月，被稱為瀝涔吹蔑之戰。昭曾率領暹羅軍隊奪路而逃，在昭披耶·阿派普貝（昭錘卞）的接應下經柬埔寨逃回暹羅，全軍只有兩千至三千人倖存。舊阮軍隊幾乎全軍覆沒，阮文威陣亡，阮福映僅率親信數人逃到鎮江，由鄚子泩接應逃入暹羅，並遣人將國母阮氏環等家眷接至暹羅。阮惠則率軍回到歸仁，留鄧文真守嘉定之地。後來嘉定成為西山朝東定王阮侶的封地。

寓居暹羅，向法國求救

阮福映逃至曼谷之後，仍有不少舊阮的支持者抗拒西山朝，但皆不是西山朝對手。後來舊阮將領阮黃德、黎文勻等人得知阮福映出奔暹羅之事，陸續前去投奔。拉瑪一世安置這些越南人於曼谷城外的平原，令其自成一個村落。這個村落當時被稱為「龍邱」（），今日的泰國人稱之為「嘉隆村」。阮福映及其部眾在這個村落裡耕種，仍懷有東山再起之志。

拉瑪一世把阮福映安置在曼谷郊外是因為看到阮福映尚有一定實力，本意是希望藉助阮福映的力量為己所用。而阮福映對此也心知肚明，因此積極參與暹羅的軍事行動。阮福映在1785年的緬暹戰爭中，派遣黎文勻、阮文誠等人參戰；此後又幫助暹羅擊退馬來海盜的騷擾。舊阮遺臣在對緬甸的戰鬥中作戰英勇，拉瑪一世大喜，厚賞之。阮福映便利用這些資金建造戰船，準備伺機復國。

而在另一方面，阮福映迫切地需要得到法國的支持。在阮福映的一再敦促下，百多祿於1785年攜其長子阮福景出發，並帶有阮福映致法國國王路易十六的書信。同時被帶去的還有阮福映的玉璽，這表明百多祿被阮福映委任為全權使者。為了能夠在越南自由傳教，百多祿盡其全力幫助阮福映復國。在臨行前，百多祿派遣西班牙籍多明我會傳教士耶妬悲、麻怒（Manuel）前去馬尼拉，試圖向菲律賓的西班牙殖民政府尋求援助，但遭西山軍扣留並殺害。

1785年2月，百多祿一行到達法屬印度的首府本地治里。但百多祿隨即發現法國對越南並不感興趣，因此派人向葡屬澳門的議院求助。1786年，葡萄牙使者來到曼谷，與阮福映簽訂了同盟條約，答應為阮福映提供了56艘西洋軍艦。翌年葡萄牙人安尊磊（António）自葡屬印度的首府果阿來到曼谷，為阮福映帶來了西式士兵和軍艦。拉瑪一世得知此事後非常不滿，阮福映為了不使拉瑪一世猜疑，被迫謝絕了葡萄牙人的援助。然而此次事件之後，阮福映不再受到暹羅人的信任。

1786年6月，百多祿一行從本地治里出發前往法國。1787年2月，百多祿一行到達巴黎，並與法國國王路易十六、海軍大臣卡斯特里侯爵、外交大臣蒙莫蘭伯爵會面。11月21日，雙方簽訂《法越凡爾賽條約》。法國承諾派遣四艘軍艦、1900名士兵前去支援阮福映；阮福映則願意割讓沱㶞（今峴港）、崑崙島給法國，並給予法國人貿易特權。同年12月，百多祿一行乘坐Dryade號軍艦離開法國，前往本地治里，準備借道本地治里歸國。但27日行至本地治里的時候，卻得知法國本土發生了極為嚴重的財政危機，政府瀕臨破產。法屬印度總督伯爵以此為由拒絕給予援助。百多祿便通過自己的關係，招募了一些法國軍官並購買一些法國武器、彈藥和軍艦。

與此同時，越南的舊阮支持者寄信給阮福映，告知了西山朝發生了內亂、阮惠與阮岳之間發生了軍事衝突之事。同時，阮福映也得知鎮守嘉定之地的都督鄧文真已率主力部隊前往歸仁的消息。1787年陰曆七月，阮福映留下書信辭別了拉瑪一世，決定率部悄悄離開曼谷。這些越南避難者計劃離開，被附近的人探知，告訴了披耶·拍康（พระยาพระคลัง，）。披耶·拍康將其報告給了拉瑪一世和二王瑪哈·素拉辛哈那。素拉辛哈那極為憤怒，親自追趕他們。黎明時分，素拉辛哈那看見了在海灣口的船隻。阮福映認為被抓獲一定性命難保，做了自殺的準備，但被身邊的人阻止。最終這些越南人成功逃脫。阮福映至富國島，被流亡越南的天地會首領何喜文迎至龍川（今金甌省）。西山朝將領阮文張率軍300人、戰船十五艘前來投奔。阮文仁等人也率舊部響應。鎮守嘉定的東定王阮侶大為恐懼，留太保範文參守嘉定，自己則退往鎮邊（今同奈、平福、巴地頭頓省一帶）。阮福映偽造了一封阮岳寫給阮侶的書信，聲稱範文參是內應，並故意將書信投遞至範文參處。範文參率軍以白旗先行，前往鎮邊，欲面白其冤。但阮侶見到白旗以後，誤以為範文參已投降，驚恐之下棄城逃往歸仁。範文參退守嘉定，阮福映圍攻，一度不能勝並損失甚重；後來武性率部前來投奔，阮福映勢力才得以恢復。1788年陰曆七月，阮福映破範文參部，重新佔領嘉定；翌年包圍範文參部於巴忒，迫其投降。至此阮福映重新在嘉定站穩了腳跟。

鞏固南方領地

阮福映在奪取嘉定之後，派阮文閑出使暹羅告捷，並對暹羅此前的幫助表示感謝。阮福映在嘉定整頓內政，禁止賭博和巫術，同時重新劃分了行政區域，制定了一系列法律，整頓稅收和農耕。阮福映推行「寓兵於農」的政策，任命鄭懷德、黎光定、吳從周、黃明慶等十二人為田畯官，勸課農桑、開墾荒地，徵不願務農者為兵。此外阮福映積極發展對外貿易，購買國外的金屬以製造兵器；同時酌情降低關稅，使得不少外國商船願意來到嘉定經商。經過了一年多的休養生息，舊阮的勢力逐漸強大。

1789年7月14日，百多祿與阮福景乘坐法國軍艦Méduse號，攜帶法式槍支彈藥返回嘉定。隨行的還有法國海軍軍官讓-巴蒂斯特·沙依諾、戴福桑、讓-馬里·達約等人。阮福映任命這些人為軍官，大規模鑄造西式兵器、軍艦，舊阮的實力又一次得到壯大。根據西方史料的記載，法國Dryade號軍官奧利維耶·德·皮曼紐爾叛逃到舊阮，為阮福映訓練步兵和炮兵，將西方先進的步兵思想帶到越南；而原為法國海軍軍官的達約、沙依諾則負責訓練海軍。至1790年，舊阮的陸軍中已有五萬名穿英國式制服、行歐洲式軍禮、裝備有西式先進武器並掌握西式戰爭技術的越南士兵；到了1792年時，舊阮海軍已擁有兩艘歐式軍艦和十五艘護衛艦。至此，舊阮無論陸軍還是海軍的實力都已經比西山軍強大，擁有絕對的優勢。

阮福映不僅從歐洲引進了先進武器和訓練方式，還按照西方的方法建造軍事堡壘。1790年，德·皮曼紐爾與西奧多·勒布朗在嘉定建立了第一個西式城堡——八卦城（又稱嘉定城堡）。

全面北伐

1790年陰曆四月，在發展有一定實力之後，阮福映派遣掌前軍黎文勻軍五千人攻打平順府。舊阮軍隊以武性、阮文誠為先鋒，輕而易舉地攻克了平順。但是由於黎文勻與武性的不和，西山軍趁機反攻，奪回了平順府，黎文勻被圍困在潘里。阮文誠率軍援救才擊退了西山軍。黎文勻因此服毒自殺。

對於日漸強大的舊阮，歸仁朝廷的阮岳聯合華南海盜，組織了一支艦隊，停泊於施耐港，準備伺機南下征討。阮福映得知後決定先發制人，1792年陰曆三月，趁著季風到來之際，阮福映派阮文張、阮文誠、達約、瓦尼埃率水軍從芹蒢海口（今胡志明市芹蒢縣）出發，突襲並焚毀了西山朝歸仁朝廷轄下施耐海口的水寨，全身而退。這場戰鬥中，由於西山軍的戰船壅塞於港口，遭到舊阮毀滅性打擊，整支艦隊只有9艘戰船倖存。身處鳳凰中都（位於今乂安省境內）的阮惠已得重病，得知阮福映勢力日漸強大後病情惡化，不久逝世，其年僅十歲的長子阮光纘繼位。

從1792年起至1799年期間，西山朝和舊阮的海軍經常利用季風的改向而對對方的領地發動進攻。舊阮海軍往往在夏季颳西南風的時候對西山朝發起進攻；而冬季到來之時，西山朝海軍便利用東北風到來之際進攻舊阮。由於當時的西山朝政治混亂民不聊生，故而每當夏天來臨的時候，西山朝轄下的百姓都盼望著東南季風的到來。

1793年陰曆三月，阮福映冊立長子阮福景為東宮，封元帥之職，鎮守嘉定。遣尊室會、阮黃德、阮文誠率步兵北伐，攻取了平順府。阮福映則與阮文張、武性率水軍攻打沿海一帶。五月，阮福映的水軍先後攻取了延慶、平康、富安三府。舊阮在延慶府建立西式城堡——延慶城，以之為重鎮。隨後舊阮的水陸兩軍會合，夾攻歸仁。阮福映率水軍來到施耐海口，西山朝歸仁朝廷的皇太子阮文寶領兵迎戰，遭到舊阮的夾擊大敗。在這場戰鬥中，舊阮軍隊第一次使用了西方的先進武器——炸彈。

歸仁朝廷君主阮岳向富春朝廷求救，阮光纘遣范公興、阮文訓、黎忠、吳文楚等人率17000名步兵和80名象兵、鄧文真率30餘艘戰船前去救援。阮福映不敵，經延慶回到嘉定，留阮文誠守延慶府、阮黃德守平順府。鑒於延慶的地勢重要，十一月又遣百多祿、範文仁、宋福溪，隨阮福景前去鎮守延慶城堡。

與此同時，西山朝富春朝廷兼併了歸仁朝廷的領地，將阮文寶降為孝公。西山朝自此在軍事上開始轉入攻勢。1794年陰曆三月，西山朝派遣阮文興攻打富安府、陳光耀攻打延慶府。阮福景、百多祿等人據守延慶城堡，抵抗在數量上具有相當大優勢的西山軍，並向嘉定求援。阮福映率大軍救援，擊退了西山軍。阮福映將阮福景等人調回嘉定，換武性鎮守延慶。翌年，武性再次成功抵擋了西山軍的進攻。

1795年，西山朝發生內亂，裴得宣、吳文楚等重臣被殺，陳光耀被罷去兵權。西山朝的將領互相猜忌殘殺，導致西山朝的實力被大大削弱。阮福映趁機發展兵備，並於1797年親征歸仁。途中突然臨時改變了策略，攻打沱㶞（今峴港）。華南海盜首領陳添保派屬下阮文伍截擊，舊阮軍隊在激戰之後被迫撤退。這次行動並不成功，因此阮福映在翌年派阮文瑞出使暹羅，請求暹羅出兵騷擾順化、乂安邊境一帶；另一方面，派吳仁靜出使清朝，希望牽制西山朝，同時探尋黎昭統帝的消息。而華南海盜則受西山朝的雇傭，騷擾舊阮轄下的沿岸，1797年陰曆七月，陳添保曾率海盜大舉入侵平康、延慶等府的沿海港口；但翌年遭到舊阮的擊敗，被迫離開這些地方。

1798年，久已不滿的孝公阮文寶據歸仁城叛亂，遣使通好於舊阮。阮福映派阮文誠前去接應，但兵未至阮文寶便被西山朝擒殺。這就是歷史上的小朝之變。這場叛亂發生之後，多疑的阮光纘聽信讒言，殺死了黎忠、阮文訓等人，導致了黎質等人的背叛，西山朝文臣武將也都離心離德。見此機會，阮福映於次年大舉北伐。西山朝派陳光耀和武文勇率陸軍支援，水軍則由被封為統兵的華南海盜首領樊文才率領。武文勇部在石津與舊阮的阮文誠部相遇，安營對峙；夜間恰巧有一隻麋鹿西山軍兵營前經過，有士兵驚呼，西山軍以訛傳訛，誤以為舊阮的同狔兵偷襲，不戰而潰。舊阮將領宋福樑擊敗了華南海盜，並與阮福映大軍合兵，合力將沿海的華南海盜巢穴逐一搗毀。歸仁城自此成為一座孤城，守將黎文清被迫獻城投降。阮福映將歸仁城改名為平定城，留武性、吳從周守城。1799年，阮福映派阮文瑞、劉福祥出使暹羅，希望調遣柬埔寨和萬象之兵攻打西山朝，得到了暹羅王拉瑪一世同意。隨後，柬埔寨攝政召華塔拉哈 (波)派兵五千人前往乂安支援阮福映。

1800年陰曆正月，西山朝派遣陳光耀、武文勇再度南下，試圖奪回平定城。華南海盜為西山軍提供了一百餘艘戰船。由於雙方兵力懸殊，西山朝大軍包圍平定城，採取圍而不攻的策略，欲迫使武性投降。阮福映親自率領八萬水軍，分乘1200艘戰船（包括4艘歐式軍艦、40艘大型戰船和300多艘大划艇）北上救援。阮福映派武彞巍、黎文悅擊退了駐守施耐海口的西山軍武文勇部，又遣阮文張粉碎了華南海盜劫奪後勤物資的圖謀，乘勝攻取了廣南、廣義兩府。阮福映派阮文瑞、劉福祥二人前往聯絡萬象。劉福祥率阮軍從萬象攻打乂安府，萬象王因塔翁（昭印）派兵四千餘人協助。北河的豪強紛紛舉兵支持舊阮。但是，舊阮軍隊始終無法衝破西山軍對歸仁的包圍圈，因此阮福映令武性棄城逃出。武性拒絕了，並建議阮福映攻打西山朝首都富春（今順化）。阮福映最終接受了武性的建議。

1801年五月，阮福映兵至思容海口，擊敗阮文治所率的西山軍。舊阮乘勝追擊，直入渜海口（今順安海口）。阮光纘親率西山軍抵抗，根據參戰的讓-巴蒂斯特·沙依諾描述，這是舊阮與西山朝之間爆發的最為慘烈的一戰，戰場上屍橫遍野。西山軍大敗潰散，支持西山朝的華南海盜也遭到舊阮軍隊的沉重打擊，重要海盜首領東海王莫觀扶以及統兵梁文庚、樊文才被舊阮俘虜。阮光纘率太宰阮光紹、元帥阮光卿、大司馬阮文賜等人，經洞海壘渡過江，逃往北河，印章璽綬全被舊阮軍繳獲。皇后黎氏玉評也被舊阮俘虜。阮福映將黎氏玉評納為昭媛。

1801年陰曆五月初三，阮福映進入富春城，張榜安民。隨後派阮文張、黎質率水步兩軍追擊阮光纘，未能追及。阮光纘逃到北河，被阮光垂迎至昇龍（今河內市），改元寶興。而陳光耀、武文勇得知富春被攻陷後，欲回軍救援，但被黎文悅部扼守道路，於是奮力攻破了平定城，武性、吳從周自殺。陳光耀、武文勇以平定城為據點，攻打周邊的舊阮城鎮，皆無功。

1802年陰曆正月，阮光纘在北河站穩腳跟之後，糾集北河的西山軍，決定同舊阮發動最後一搏。與此同時，華南海盜首領鄭七原已離開越南回到廣東，在陳添保的勸說之下，率屬下分乘200艘戰船前往北河，表示效忠於西山朝。鄭七抵達昇龍後，被阮光纘封為大司馬。但旋即陳添保認定西山朝敗局已定，棄官逃往中國，向清廷投降。得到鄭七的支持之後，阮光纘隨即親率大軍三萬南下，來到江，派鄭七守日麗海口（日麗江入海口）。舊阮將領阮文張、鄧陳常不敵，退往洞海（今廣平省洞海市）。阮福映聞報，親自率大軍北上，遣範文仁、鄧陳常守陸路，阮文張守水路。阮光纘派阮光垂圍攻鎮寧壘（又名洞海壘、日麗壘，位於今廣平省），久攻不克；阮文張則在此期間突襲日麗海口，大破鄭七率領的華南海盜。圍攻鎮寧壘的西山軍驚恐之下潰散，阮光纘逃回昇龍。身處平定城的陳光耀、武文勇，得知阮光纘戰敗後，率軍棄城北上欲與之會合，但途中被舊阮擊敗並俘虜。

滅亡西山朝

嘉隆元年五月初二日（1802年6月1日），阮福映宣佈停止使用後黎朝的年號景興；改用新年號「嘉隆」。自此越南歷史上最後一個封建王朝——阮朝自此誕生。勢力日薄西山的阮光纘還希望藉助清朝的力量對抗舊阮，派遣阮登為使者，前往清朝求援。阮福映則於此時派遣鄭懷德、吳仁靜出使清朝，獻上繳獲的西山朝印綬，並將被俘虜的海盜首領莫觀扶、梁文庚、樊文才三人移交清廷。兩廣總督吉慶審問了三人，得知西山朝一直支持華南海盜的事實，將此呈報清廷。嘉慶帝聞報後勃然大怒，下令驅逐西山朝使者，並命令吉慶將莫觀扶、梁文庚、樊文才三人按大逆罪淩遲處死。

隨後阮福映親率大軍北伐，清化督鎮阮光盤獻城投降。阮朝軍隊以摧枯拉朽之勢向北推進，並迅速攻佔昇龍。阮光纘率宗室大臣逃跑，在鳳眼縣被農民俘虜，六月二十三日送至昇龍。阮福映下令免除北河百姓一年的稅收。阮福映任命阮文誠為北城總鎮，管理當地事務；又在北城設置戶曹、兵曹、刑曹職務，分別由阮文謙、鄧陳常、範文登擔任。阮福映還讓後黎朝的後裔黎維主持後黎朝皇室的祭祀，鄭主的後裔鄭楈主持鄭主家族的祭祀，以安撫他們的支持者。

陰曆七月，阮福映率軍回到順化，押解西山朝君臣至順化太廟行獻俘之禮。阮光纘及西山朝宗室阮光維、阮光紹、阮光盤等淩遲處死之後五象分屍；武將武文勇、陳光耀等梟首示眾；文臣吳時任、潘輝益等則被押往北城河內，在河內文廟前施以鞭刑，然後釋放。阮福映又聲稱「朕聞為九世而報仇」，下令將阮岳與阮惠的屍體從墳墓中掘出，搗棄其骸骨；並將阮岳、阮惠的頭骨和阮惠夫婦的木主處以「幽禁外圖家」的處罰。明命二年（1821年），改為「永禁監獄室」。

整頓內政

阮光纘在位期間政局動盪不安，政治腐敗。因此阮福映在奪取政權之後，下令改革政治制度。1815年，阮福映參照中國的《大清律》，頒佈了《嘉隆律書》。

地方行政

阮福映將越南全境分為北城、嘉定城以及朝廷直轄區域三個部分。其下又分為23鎮4營。

• 北城下轄11鎮：山南上鎮（今興安大部、河南、河內東部）、山南下鎮（今南定、太平兩省）、山西鎮（今河內市西部和永福大部、富壽東部）、京北鎮（今北江、北寧兩省、河內北部）、海陽鎮（今海防市和海陽省）、宣光鎮（今宣光、河江兩省）、興化鎮（今富壽西部、老街、山羅、和平、萊州、奠邊等西北省份，包括今寮國部分領土）、高平鎮（今高平省大部）、諒山鎮（今諒山省）、太原鎮（今太原、北𣴓兩省）、安廣鎮（今廣寧省）；

• 嘉定城下轄5鎮：藩安鎮（今胡志明市）、邊和鎮（今同奈、巴地頭頓、平福一帶）、永清鎮（今永隆、安江一帶）、定祥鎮（今前江、堅江、檳椥、茶榮一帶）、河僊鎮（今金甌省及富國島一帶以及柬埔寨西哈努克市）；

• 阮朝朝廷直轄7鎮：清華鎮（今清化省）、乂安鎮（今乂安、河靜兩省）、廣義鎮（今廣義省）、平定鎮（今平定省）、富安鎮（今富安省）、平和鎮（今慶和省）、平順鎮（今平順、寧順兩省）；

• 京畿直轄4營：直隸廣德營（今承天順化省）、廣治營（今廣治省）、廣平營（今廣平省）、廣南營（今峴港市和廣南省）；

其中，京畿由阮朝朝廷直接管理，北城和嘉定城分別設置總鎮和副總鎮（或稱協鎮）以管理事務。北城和嘉定城的總鎮都是由立下赫赫戰功的武將擔任。各鎮以留鎮或鎮守為長官，鎮之下又細分為府、縣、州，由知府、知縣、知州為長官。

阮福映也意識到北城這片剛佔領的領地形勢錯綜複雜，既存在有支持後黎朝和鄭主勢力的餘黨，也存在著據守山區、朝廷難以管理的土豪，而且這些勢力依然強大。阮福映認為北城地區「民性驕頑」，難以統治，因此並沒有遵循前代歷朝定都河內的慣例，而是將都城選在了歷代阮主的統治中心順化。1803年，阮福映命黎質、範文仁、阮文謙，參照中國紫禁城的建築風格，在富春城內修建順化皇城，作為阮朝朝廷的行政中心。

對於北城存在的各種勢力，阮福映決定任命他們為官。北城的11鎮被分為內五鎮和外六鎮，內五鎮由後黎朝舊臣管理，外六鎮由地方土豪管理。這種委任地方勢力為官的制度直到明命帝繼位的時候才被廢止。

阮福映在位期間，參照法國的沃邦式城堡的建築風格，在越南全境又先後建立了9座城堡。這些城堡分別是北城轄下的榮市、清化、北寧、河僊，朝廷直轄地的順化、廣義、慶和、平定，以及嘉定城轄下的永隆。德·皮曼紐爾和西奧多·勒布朗在戰爭結束之後離開了越南，越南工程師們參照他們建造八卦城和延慶城堡時用的建築圖紙，建造了這些城堡。阮福映認為國家剛剛步入安定時期，百姓容易受朝廷調遣；若再過數年，百姓便習慣於安逸生活，那時再徵調他們建造大型工程，就很容易引起百姓的不滿。故而他在位期間大興土木，建造了眾多工程。他還積極修建官道、修建驛站、疏通河流、建立堤壩。

軍事制度

阮福映滅西山朝之後，賞賜有功將士，允許年老體弱者卸甲歸田。又賞賜並修建廟宇，祭祀陣亡將士。他制定了兵丁之法：廣平至平順各鎮三丁抽一，邊和以南各鎮五丁抽一，河靜以北、北城內鎮七丁抽一，北城外鎮十丁抽一。京畿一帶設立親兵、禁兵、精兵，統稱三兵，以守衛順化。各鎮設立奇兵、募兵，分作三番輪流值班。阮朝設置五軍都統府，其首領由皇帝的親信擔任。若要動用軍隊，則由五軍都統率兵出征。

而在兵器上，阮朝軍隊使用的主要是劍槊、馬刀以及銅制大炮，也有使用西洋的槍支鳥銃。阮朝在順化設立三個射擊場士兵每年進行一次射擊演習。但阮朝朝廷對西洋槍支的使用非常苛刻，每隊50人中只有5人擁有鳥銃，每人每年只允許使用六發子彈，超過數目者要賠償。

阮福映非常重視海港的軍事防備，在各港口都建立炮臺，檢查過往船隻；又建造了巨大的船隻以巡防海面。而對於活躍於南中國海沿岸的華南海盜，阮福映持嚴厲打擊的態度。1802年，就在阮福映推翻西山朝後不久，阮朝官軍便攻陷了華南海盜位於江坪（今中國廣西壯族自治區東興市江平鎮）的大本營，將著名的海盜首領鄭七俘虜並斬首。此後官軍清剿華南海盜在越南沿海一帶根據地，華南海盜勢力遭受沉重打擊，不得不離開越南，回到中國廣東一帶發展。

經濟制度

在財政稅收上，阮福映重新規定了丁稅、田稅的相關法律。阮朝將全國的田地分為三等，按田地質量的優劣來衡量田稅徵收的多少。若地方遭遇自然災害，或者國家徵用壯丁修路、挖河、建城等，則酌情減稅。阮福映制定了丁簿、田簿制度，地方每隔五年對壯丁（18歲以上、59歲以下男性）、田地進行一次調查並編製成冊。阮福映頒佈法律，禁止了後黎朝時期盛行的買賣公田的行為，但准許在應急的時候租借公田使用三年；超過期限不還者要受到法律的懲罰。

阮福映還制定了商稅和礦稅，以及香、參、席、木、燕窩等稅收。朝廷規定商稅按照船舶的大小來徵收。

嘉隆帝在位時期，阮朝直轄領地、北城外鎮、北城內鎮所規定的稅收標準不同，但都由朝廷制定；而嘉定城的稅收標準則由嘉定總鎮確定。

1803年，阮福映先後在順化、河內、嘉定開設鑄錢爐，鑄造嘉隆通寶。1810年製造丈量土地的標準銅尺並頒發給地方；1813年，又製造平天衡發給各營各鎮。

官僚制度、法律制度

1811年，阮福映下令廢除後黎朝的《洪德律》，命阮文誠為總裁，主持編纂新的律書。阮文誠等人參照中國的《大清律》，編成《嘉隆律書》（當時稱為《皇朝律例》）二十二卷，共計398條。1815年，阮福映將此律書頒行各地。

越南歷史學家陳仲金認為《嘉隆律書》是在《大清律》上做些許修改之後頒行的。越共學者則認為，《嘉隆律書》宣揚婦女的三從四德和皇帝的絕對權力，「極其保守和頑固」，是「反動」而「退步」的。

在官僚制度上，阮朝沿用了後黎朝的六部制度，各部以尚書為長官，下設參知、侍郎、郎中、員外郎、主事等官。又設督察院以勸諫皇帝、彈劾大臣。

而對於宮中的事務，阮福映定下了皇帝生前不立皇后的規矩。宮中只設有皇妃和宮嬪，按等級分為一階至九階；皇帝駕崩之後，嗣君繼位，才尊其母為皇太后。皇太后死後，追贈皇后的稱號。

對於爵位，阮福映規定不得封異姓大臣為王爵。皇子雖可以封王，但不能擁有實權。

科舉與學術

阮福映是通過暴力手段奪取政權的，因此阮福映手下的重臣多是武將出身。但阮福映意識到治理國家也需要文臣，因此在阮朝建立之後，阮福映恢復了被西山朝廢除的科舉制度，在全國各地建立文廟，在順化設立國子監，推行儒學，教授四書五經。

阮福映也關注越南地理書籍和國史的編纂。《皇越一統輿地誌》、《大南會典事例》等書便是奉阮福映之命編纂的。《大南實錄》也開始編纂。阮福映在位期間，也是越南文學發展的時期，湧現出大量包括字喃文學在內的詩歌小說，《大南國史演歌》以及著名的《金雲翹傳》都是在這個時期問世的。

宗教政策

阮福映推崇儒家思想。而東宮阮福景在西方思想的燻陶下更傾向於基督教，這令阮福映很不滿。因此，在阮福景生前，阮福映曾與他多次發生思想上的衝突，有時候阮福映甚至大發雷霆。但是，阮福映仍然遵守之前的諾言，允許西方傳教士在越南自由傳教。嘉隆年間，共有六名傳教士來到越南活動，這些人來自法國或西班牙。當時北城轄境內共有三十萬名基督徒，而嘉定城境內有六萬名。但是阮福映竭力推崇儒家思想以限制基督教的傳播。

此外，雖然宮中的後妃多信奉佛教，但阮福映在政策上對佛教也進行了限制，他頒佈法律，禁止民間對祭祀神佛的活動大操大辦。

外交政策

• 與法國的關係：百多祿試圖讓阮福映與西方國家接近並貿易，但隨著1799年百多祿的死而以失敗告終。法國皇帝拿破崙一世有征服越南的野心，他希望將越南作為法國在遠東的殖民地以抗衡英國在印度的霸權。但拿破崙忙於在歐洲打仗，無暇東顧，後來也隨著拿破崙的被流放而不了了之。波旁王朝復闢之後，法國首相黎塞留公爵派Cybele號來到沱㶞港（今峴港），向阮朝朝廷贈送了一艘配備有52支槍的護衛艦作為禮物，還轉交了法國國王路易十八的國書，希望阮福映踐行他在《法越凡爾賽條約》中的承諾。但阮福映認為自己並沒有得到法國的實際援助，故而拒絕了法國的要求，卻其國書並且退回了法國的禮物。

• 與英國的關係：1804年，英國人約翰·羅伯茨（John Roberts）來到越南，要求在廣南的茶山建立商館。由於阮福映曾在馬德拉斯和加爾各答從不列顛東印度公司那裡購買武器，為了信守諾言，阮福映給予了英國一定貿易特權。但建立商館的要求遭到拒絕，英國的禮物也被退回。1822年，明命帝終止了英國人的貿易特權。

• 與中國的關係：1803年，阮福映派遣鄭懷德、黎光定出使清朝請封。阮福映取「安南」的「南」字、「越裳」的「越」字，請求清朝賜國號「南越」；但嘉慶帝將其改為「越南」，這就是今日越南國名的由來。嘉慶帝認為歷史上「南越」之地較廣，兩廣（廣東與廣西）皆在其內；阮福映全有安南，亦不過是交趾故地，故而將其二字順序顛倒。不過，清朝回覆安南時稱，以「越」字冠於「南」字之前，表示阮福映先繼承越裳之地，而再開拓疆域於安南，不僅名稱正大、字義吉祥，又能與兩廣的舊稱「南越」相區別開來。次年，嘉慶帝派遣廣西按察使齊布森出使越南，冊封阮福映為越南國王，頒賜越南國王金印一枚。阮福映來到昇隆（今河內）接受清朝的冊封，隨後遣黎伯品充如清正使，陳明義、阮登第充甲乙副使，前往清朝進貢並謝恩，雙方約定三年一貢為慣例。1806年，阮福映正式舉行登基大典，確定新國號「大越南國」。但原國號「大越」仍被使用，直至1839年被明命帝廢止。

• 與暹羅的關係：阮福映即位前曾流亡暹羅，暹羅曾於1784年出兵越南，試圖協助他復位，但失敗。後來阮福映趁西山朝內亂之機回到越南，重新佔據了嘉定，以此為基地進行北伐並最後統一全國。根據泰國《拉達那哥欣皇家編年史》記載，在阮福映稱帝之前，曾先後六次向暹羅王拉瑪一世進貢金銀花，以表示臣服之意。在北伐西山朝的戰爭中，阮福映曾派人向暹羅請求調遣柬埔寨、萬象的士兵，得到拉瑪一世的同意。阮福映建立阮朝以後，不再向暹羅進貢金銀花，但仍與暹羅互相派遣使者。1813年，阮朝曾與暹羅因柬埔寨問題而發生衝突，但在嘉隆年間雙方總體上保持著友好往來的關係。

• 與柬埔寨的關係：1779年，阮福映將柬埔寨變為附庸國；但在1782年嘉定被阮惠攻陷之後，舊阮喪失對柬埔寨的控制。不久，柬埔寨發生內亂，國王安英（匿印）出奔暹羅。拉瑪一世乘機將其扣留，並派昭披耶·阿派普貝監督柬埔寨內政。1796年安英逝世時，暹羅不准其子安贊二世（匿螉禛）歸國繼位。直到柬埔寨攝政召華塔拉哈 (波)去世後，方才冊封安贊二世為王。安贊二世不滿於暹羅的統治，在外交上遊走於越南和暹羅之間。1807年棄暹羅向越南朝貢。這侵犯了暹羅的利益，1811年，暹羅暗中扶持安斯農（匿螉原）叛亂。安贊二世逃往嘉定城，向阮朝朝廷求救。1813年，阮福映遣黎文悅攜安贊二世歸國復位，並駐兵南榮（今金邊）、盧淹（今幹丹省勒維恩縣）兩城，將柬埔寨重新變為越南的附庸國。安斯農出奔暹羅，暹羅駐軍於今馬德望省一帶，欲以該地區封安斯農為王。黎文悅作書譴責暹羅，暹羅與越南達成和解之後撤離了該地。在阮福映在位期間，越南與暹羅沒有發生過正面的軍事衝突，而柬埔寨則同時向越南和暹羅朝貢。

• 與琅勃拉邦的關係：琅勃拉邦王國（南掌）此前曾發生王位糾紛，故王之子曼古·拉加古曼（Ong Manhku Rajakoumane，溫猛）與國王阿努魯塔（𦵚乍）爭奪王位。曼古獲得清朝的承認和冊封，進攻阿努魯塔，戰敗後逃往興化的昭晉州（今萊州省封土縣）投奔當地土司。1802年秋，曼古來昇隆（今河內）朝見阮福映。阮福映認為天下初定，沒有時間處置這件事情，讓他回昭晉州。與此同時，阿努魯塔遣使，請求從寧邊州（今奠邊府市）入貢。1809年，曼古又被北城臣送來順化。阮福映將他送往諒山的鎮南關（今中越邊境友誼關），讓清朝處置。清朝認為曼古不能自立，拒絕了他的王位請求並沒收其敕印。此後，曼古客居昭晉州直至逝世。

• 與萬象的關係：阮福映早在流亡暹羅期間就與萬象王國（zh-hans:万象;zh-hant:萬象;）國王因塔翁（昭印）相識。在北伐西山朝戰爭期間，萬象曾出兵配合。阮朝建立的時候，因塔翁遣使入貢，阮福映命令將川壙（鎮寧）之地隸屬於萬象。因塔翁去世後，暹羅立因塔翁之弟昭阿努（阿弩）為萬象王。阮福映派該奇阮文蘊、翰林黎文富前往萬象賜賻。川壙發生王位繼承權的鬥爭，在阮朝與萬象的支持下，昭內登上了川壙王位。

誅殺功臣

根據史料記載，阮福映在晚年性格多疑，常對大臣起猜忌之心。而一些朝中大臣之間有互有嫌隙，因此鄧陳常、阮文誠等一些功臣遭到殺害。

鄧陳常在阮福映還在嘉定期間便前去投奔，隨其顛沛流離，後因戰功逐漸升遷，任北城兵曹，後又任兵部尚書。兵部尚書任內，因將鄭主部將黃五福列為福神被人告發而失勢。黎質與其有仇，1813年，趁機告發其在北城兵曹任內的不法之事，阮福映下令將鄧陳常罷官下獄。鄧陳常甚為不滿，在獄中作《韓王孫賦》一首，自比為漢朝的韓信。阮福映大怒，欲殺鄧陳常，皇子阮福膽力救不能免。阮福映令鄧陳常自殺，但鄧陳常不從，遂被絞死。

阮文誠也是阮福映的舊臣，此人文武雙全，在征討西山朝的戰鬥中立下赫赫戰功。阮朝建立後擔任北城總鎮，之後回京任中軍之職，《嘉隆律書》也是此人主持編纂的。但他與另一重臣黎文悅有仇，阮文誠曾派人暗殺黎文悅，但未成功。1817年，阮文誠之子阮文詮寫了一首頗為自大的詩，黎文悅便告發阮文詮有謀反之心。於是阮文誠被逮捕入獄。阮福映命黎文悅審問阮文詮，黎文悅強迫阮文詮認罪。於是阮福映迫使阮文誠飲毒藥自盡，其子阮文詮處斬。

晚年及逝世

在阮福映建立阮朝之後，仍有法國人沙依諾（阮文勝）、瓦尼埃（阮文震）、德斯皮奧以及巴里西等人在朝中擔任高官。阮福映給予他們特殊的待遇，賜予他們50名衛兵，准許上朝時免行跪拜之禮。雖然阮福映對他們禮遇有加，但他們都感到鬱鬱不得志。阮福映逝世後不久，沙依諾便向繼任的明命帝提出辭官告假三年，返回了法國。此後法國籍官員也陸陸續續提出辭職，黯然歸國。

1801年阮福景逝世後，雖然按照慣例應該由阮福景的長子阮福美堂擔任皇嗣孫，但由於阮福景一系有強烈地親西方和基督教傾向，且阮福美堂尚未成年，故而阮福映遲遲不立繼承人。1815年，阮福映立推崇儒家思想的庶子阮福膽為皇太子，將阮福景一系的子孫排除在了皇位繼承權之外。

雖然阮福映在奪取皇位的過程中受到西洋人的幫助，但他認為西洋人「非我族類，其心必異」，對西洋人存在有相當大的戒心。然而他也看到了阮福膽的內心具有強烈地排外和反基督教傾向，故而告誡阮福膽，要求他要尊重歐洲人特別是法國人，但不要給予他們任何優待，更不能把土地割給法國。

1820年2月1日（嘉隆己卯年臘月十七），阮福映病重，召皇太子阮福膽、諸皇子、諸公以及大臣黎文悅、范登興入宮，宣佈了遺詔，任命黎文悅、范登興為輔政大臣。臘月十九，阮福映駕崩，在位18年，壽58歲。陰曆正月初一，皇太子阮福膽改名阮福晈並正式繼承皇位，是為明命帝。

阮福映死後廟號世祖（），諡號開天弘道立紀垂統神文聖武峻德隆功至仁大孝高皇帝（）。其遺體被合葬於其原配宋氏蘭之陵寢，葬於宋氏蘭墳丘的左側，兩陵寢統稱天授陵。

形象

阮福映擅於使用鳥鎗，發無不中。他也愛好讀書尤其是史書，在位期間曾多次要求下詔讓民間獻書。

阮福映的性格直率而果斷，文臣武將往往能在他面前直接表露出自己內心的想法。他不僅喜愛宮廷舞蹈等士大夫的愛好，也喜愛鬥雞、㗰劇等越南民間的愛好。在私下場合他會表現出平易近人。據說黎文悅曾在他面前開玩笑地就鬥雞問題發表長篇演說。

阮福映用人不重視出身，如：朱文接出身馬商，黎文悅出生農民。他也不重視其種族，其部將有眾多外國人，如：法國人沙依諾、瓦尼埃、達約、皮曼紐爾、戴福桑、勒布朗等人，高棉人阮文存，中國人何喜文、黃忠仝、張公引，還有暹羅人溫利·馬盧（Vinhly Malu，榮麻離）。投降的部將只要有才能也受重用。

阮福映也是個守信的人。他信守自己的諾言，允許傳教士在越南自由傳教，還給予英國人貿易特權，雖然他並不情願這麼做。他死後，明命帝便遵循其遺訓廢除了英國的貿易特權，後又發佈禁教令。

而在當時的西方，阮福映則被宣傳為基督教徒的庇護者，西方人認為他推動了基督教在越南的傳播。而事實上阮福映偏向於儒家思想，在內心裡對基督教比較抵制。

評價

• 西山朝君主阮惠把阮福映看作是西山朝的最大禍患。阮惠臨終時，阮福映勢力日漸強大，因此阮惠對西山朝的未來非常擔憂。

• 法國傳教士古拉爾（Guérard）認為：「嘉隆王用一切手段敲榨人民，不公正和橫行霸道，使得人民比西山時期更加痛苦。賦稅和勞役增加三倍。」

• 阮朝維新年間編纂的《國朝正編撮要》，對阮福映作如是評價：「帝中興創業，功德兼隆，鴻厖以降未之有也。立國之始，營城郭，修陵寢，建郊廟、社稷，班爵制祿，開科取士，興禮樂、學校，定法度、條律，存黎、鄭之後，延功臣之世，郤西山之獻，密暹羅之防，懷真臘，撫萬象，威震殊方，仁覆小邦，規模葢宏遠矣。」

• 越南歷史學家陳仲金認為，阮福映是一位「具有才智的國君，聰明睿智，在長達25年的時間之內與西山相抗，經歷了無數艱難險阻，但何時候也未曾灰心喪氣，而仍一心一意思慮復國大業。」；陳仲金又評價阮福映「頗具創大業之美德，知人善任，使豪傑之士人人都忠心耿耿為之效忠命」，「因此他不僅恢復了舊業，而且還統一了山河，進行諸項改革，使當時的我國成為一個空前未有的強大國家」；但是對於阮福映晚年殺害功臣之事陳仲金也提出批評，認為他像漢高祖一樣濫殺功臣。

• 越共對阮福映的評價非常差，認為他發動「反革命戰爭」，依靠外國勢力鎮壓農民起義，建立了越南歷史上最後一個而且是最「反動」的封建王朝。對於其即位之後的各項改革越共也都評價不佳，認為其最終目的都是「鎮壓人民的反抗」。

• 中國學者郭振鐸、張笑梅認為，阮福映在世「既有過又有功」，但是「過大於功」。他藉法國之助（此中國學者說法有誤，法國當時爆發大革命，根本沒有前來支援嘉隆帝，嘉隆朝的法國人等諸多國籍的外國人是嘉隆帝依據才能招募而來）鎮壓西山起義，「為法國進入越南並將越南變成法國殖民地奠定了基礎」；他在位期間對外侵略柬埔寨，對內「專制獨裁，壓迫人民」，晚年又殺害功臣，因此其過匪小。而他的功勞在於「將動亂分裂的越南社會歸於統一」，之後又施行一系列改革，「對越南封建社會發展起了一定推動作用」。

家庭

後宮

子女

包括未序齒的子女在內，阮福映有子19人，女18人。

注釋