The Cambodian uprising of 1840–1841 was a general uprising of Khmer people against direct Vietnamese rule in September 1840. In response to Siamese invasion of Cambodia and Southern Vietnam in 1833, the Vietnamese Nguyen dynasty had annexed Cambodia into Trấn Tây Province in 1835 with Ang Mey as puppet female ruler under Trương Minh Giảng. Vietnamese rule over Cambodia was established with the consent of the pro-Vietnamese faction in Cambodia in order to repel and eliminate any Siamese influence or incursions into Cambodia but friction between the Khmers and the Vietnamese eventually led to the general uprising against Vietnam.
Not all of Cambodia was under Vietnam's Trấn Tây Province. Siam had earlier appropriated northwestern Cambodia, including Battambang and Siemreap, into its own direct rule in 1794. The Siam-held northwestern Cambodia, known in Thai historiography as Inner Cambodia, centered on Battambang, had been serving as the base for expansion of Siamese interests in Cambodia. Through this period of Vietnamese rule, the Siamese at Battambang had been looking for a ripening opportunity to reassert their domination over Cambodia. Defection of Cambodian Prince Ang Em from Siamese to Vietnamese side in 1839, dethronement of Queen Ang Mey, exile of Cambodian royalty and high-ranking Cambodian ministers in 1840 dissatisfied Khmer people, who viewed the Vietnamese as eroding their cultural identity and traditional governance. This Cambodian uprising against Vietnam in 1840 enabled Siam to push forward its candidate Prince Ang Duong for the Cambodian throne, instigating the Khmers to rise against the Vietnamese.
Cambodian uprising of 1840–1841 undermined Vietnamese position in Cambodia, allowing the Siamese armies under Chaophraya Bodindecha to march into Cambodia in November 1840 to take control of Cambodia, leading to the Siamese–Vietnamese War of 1840–1841. In spite of their precarious position, the Vietnamese still held out against the invading Siamese. Death of the Vietnamese Emperor Minh Mạng in 1841 spelt the end to Vietnamese rule in Cambodia as the new Vietnamese ruler Thiệu Trị favored withdrawal of Vietnamese troops from Cambodia. Thiệu Trị ordered the general retreat of the Vietnamese from Cambodia in late 1841, thus ending the six-year direct rule of Vietnam over Cambodia. Vietnamese withdrawal allowed the Siamese to take control over Cambodia, bringing Cambodia into another period of Siamese domination.
This Cambodian uprising against Vietnamese rule during 1840–1841 was a rare example of pre-revolutionary nationwide Cambodian uprising, comparable to that of Cambodian uprising against French rule in 1885–1886 and the 1916 Affair. For many years, the Siamese and the Vietnamese, aided by competing Cambodian factions, would battle in Cambodia, devastating Cambodia to the degree not to be achieved until the Cambodian Civil War of the 1970s.
Background
Cambodia under Vietnamese domination
In 1794, King Rama I of Siam sent the young Cambodian king Ang Eng to rule in person after twelve years of refuge or captivity in Bangkok. The Siamese king Rama also separated northwestern Cambodia including Battambang and Siemreap to be under Chaophraya Aphaiphubet Baen the first Siam-appointed governor of Battambang under direct Siamese rule. King Ang Eng of Cambodia died in 1797, leaving four sons Ang Chan, Ang Sngoun, Ang Em and Ang Duong. King Rama I considered the princes too young to rule so he did not enthrone a new King of Cambodia until 1806, when the Siamese king eventually allow Ang Chan, eldest son of Ang Eng, to become the new King of Cambodia. However, Ang Chan, given his negative experiences with the Siamese court, became weary of Siamese domination over Cambodia and sought out for Emperor Gia Long of the Vietnamese Nguyen dynasty to counter Siamese influence. When King Rama I of Siam died in 1809, Ang Chan defied the Siamese right away, refusing to go to attend the funeral of the deceased Siamese king at Bangkok, sending his younger brothers Ang Sngoun and Ang Em to go in his stead. The new Siamese king Rama II made Ang Sngoun and Ang Em the Uprayorach (Second King) and the Ouparach (Third King), respectively, without consulting Ang Chan, turning Ang Sngoun into a pro-Siamese rival of Ang Chan.
Ang Sngoun, younger brother of the incumbent King Ang Chan of Cambodia, rebelled at Pursat in 1812. The Siamese marched from Battambang into Cambodia to support Ang Sngoun, prompting Ang Chan to flee to take refuge at Saigon under Vietnamese protection. During the flight, Ang Em and Ang Duong, younger brothers of Ang Chan, decided to join the Siamese instead. The Siamese destroyed and burnt down the Cambodian royal capital of Oudong, which stood as the capital of Cambodia for two centuries, in early 1813 and took the three Cambodian princes Ang Sngoun, Ang Em and Ang Duong to live at Wang Chao Khamen or Cambodian quarters in Bangkok. Emperor Gia Long of Vietnam sent Lê Văn Duyết the Tổng trấn (總鎮) governor of Saigon and Viceroy of Cochinchina to march Ang Chan back to Cambodia in 1813, restoring Ang Chan to rule. As the royal capital was destroyed by the Siamese, Lê Văn Duyết built a new citadel at Phnom Penh called Banteay Keav for Ang Chan to reside as his capital. In 1814, Gia Long appointed Nguyễn Văn Thoại as bảo hộ or Protector of Cambodia, essentially the Vietnamese representative minister in Cambodia. The dynastic conflict of 1812–1813 shifted Cambodia from Siamese to Vietnamese domination as Siam lost control over Cambodia to Vietnam but Siam was waiting for the right moment to reclaim its control over Cambodia.
In 1819, Emperor Gia Long initiated a grand construction project of the Vĩnh Tế canal that connected Châu Đốc with Hà Tiên in Southern Vietnam bordering Cambodia. Emperor Gia Long died in early 1820, succeeded by his son Minh Mạng. In August 1820, a Cambodian Buddhist monk named Ke declared himself a Neak Sel or holy magician man, rallying Khmer people to rise against Vietnamese domination, leading to the Cambodian Uprising of 1820. Ke and his forced killed the governor of Ba Phnum and established themselves there. The Cambodian king Ang Chan, being under Vietnamese influence, was obliged to send forces under Chauvea Tolaha Tuan Pha (Cambodian Prime Minister of Cham ethnicity) and Samdech Chauponhea Tey to suppress this rebellion. However, Oknha Noren Kol defected to the rebel side and the royal forces were defeated. Lê Văn Duyết the governor of Saigon sent Nguyễn Văn Trí to bring Vietnamese forces to defeat and kill Ke at Koh Sotin, dissolving Ke's movement. Noren Kol and other followers of Ke were arrested and interrogated. They confessed it was the Cambodian ministers Chauvea Tolaha Tuan Pha and Samdech Tey that had instigated them to aid the rebels in the first place. Tuan Pha, Samdech Tey and Noren Kol were eventually executed.
In November 1820, King Ang Chan wrote to Lê Văn Duyết at Saigon, asking to resume the joint Cambodian–Vietnamese Vĩnh Tế canal construction project. 39,000 Southern Vietnamese and 16,000 Khmer men were conscripted to dig the canal day and night. The construction of the Vĩnh Tế canal was eventually finished in 1824. In the same year, King Chan of Cambodia offered three districts of Prey Kabbas (Lợi Kha Bát), Choan Chum (Chân Sum) and Moat Chruk (Mật Luật) and as a personal gift of gratitude to Nguyễn Văn Thoại the Vietnamese Protector of Cambodia. Minh Mạng told Nguyễn Văn Thoại to accept only two districts of Chân Sum and Mật Luật. Nguyễn Văn Thoại died in 1829 and Lê Văn Duyết also died three years later in 1832. Lê Văn Duyết had been the Tổng trấn or powerful Viceroy of Saigon, holding power over Southern Vietnam and Cambodia. Death of Lê Văn Duyết prompted Minh Mạng to enact administrative reforms in 1832 including the abolition of Tổng trấn in favor of Tổng đốc (總督). The Tổng đốc An Hà or governor of An Giang and Hà Tiên provinces would concurrently held the position of bảo hộ or Protector of Cambodia. In late 1832, Lê Đại Cương was appointed as the governor of An Giang and Hà Tiên, also Protector of Cambodia at the same time.
Siamese Invasion of Cambodia (1833)
In 1833, the new officials installed in Southern Vietnam by Emperor Minh Mạng reported that the late viceroy Lê Văn Duyết had been plotting a rebellion. Minh Mạng issued punishments to the associates of Lê Văn Duyết, prompting his adopted son Lê Văn Khôi to kill Minh Mạng's officials and rebelled at Saigon. In 1833, Vietnam was embroiled in three rebellions; Lê Duy Lương Rebellion in Nghệ An province, Le Van Khoi Rebellion at Saigon in the Southern Vietnam in Cochinchina and Nông Văn Vân Rebellion in Cao Bằng province in the Northern Vietnam. Taking advantage of unstable situation in Vietnam, Siam saw an opportunity to reclaim control over Cambodia and possibly to conquer Southern Vietnam. In November 1833, King Rama III of Siam, with the goal of establishing the pro-Siamese candidates Ang Em and Ang Duong to power in Cambodia and also conquering Saigon, sent Siamese armies to invade Cambodia and Southern Vietnam;
Chaophraya Bodindecha the Samuha Nayok or Prime Minister of Siam led the Siamese forces of 40,000 men (posthumous publication) to invade Cambodia by land from Battambang, going through Cambodia to attack Saigon. Chaophraya Phrakhlang, personal name Dit Bunnag, the Minister of Trade, led the Siamese fleet of 10,000 men from Chanthaburi to attack Hà Tiên by sea, going through the waterways of Mekong Delta to attack Saigon.
Alarmed by Siamese invasion, King Ang Chan of Cambodia dispatched his War Minister Oknha Chakrey Long to defend Cambodia but Chakrey Long could barely raise an army due to manpower shortage, unable to stop the Siamese at Kampong Chhnang. Ang Chan had to flee from his capital Phnom Penh to take refuge at Vĩnh Long in Cochinchina. Chaophraya Bodindecha and his Siamese armies marched through Cambodia with ease. Chaophraya Phrakhlang Dit Bunnag attacked Hà Tiên, surprising the Vietnamese, who were unprepared and concentrating on putting down the rebellion at Saigon. Bodindecha assigned Ang Em and Ang Duong to occupy the Cambodian royal capital of Phnom Penh at Banteay Keav. Two Siamese army routes of Bodindecha and Phrakhlang converged at Châu Đốc, where they proceeded downstream the Bassac River, going towards Saigon. However, the Vietnamese Emperor Minh Mạng allocated some troops from Saigon under Nguyễn Xuân, Trương Minh Giảng and Lê Đại Cương to face the invading Siamese.
The Siamese and the Vietnamese fought in the Battle of Vàm Nao in January 1834, in which the Vietnamese prevailed and the Siamese were defeated. The Battle of Vàm Nao turned the tide of war in favor of the Vietnamese. In his retreat, Chaophraya Bodindecha resorted to rounding up as many Khmer people as possible as captives in order to make up for the Siamese defeat. Bodindecha commanded the Princes Ang Em and Ang Duong to destroy Banteay Keav, the royal citadel of Phnom Penh. The Siamese suffered further from guerilla attacks of the Cambodians under Oknha Chakrey Long and Oknha Yomreach Hu, who preyed on the panicked retreating Siamese. Vietnamese commanders Nguyễn Xuân and Trương Minh Giảng and the Cambodian War Minister Chakrey Long pursued the Siamese to the edges of Cambodian territory. By April 1834, the Siamese had all retreated, with Bodindecha retreating to Battambang and Phrakhlang to Chanthaburi.
With the Siamese gone, the refugee king Ang Chan was paraded by the Vietnamese to return to Phnom Penh, where he found his residence, the citadel of Banteay Keav, built by Lê Văn Duyệt for him in 1813, destroyed and burnt down by the Siamese. Ang Chan built himself a temporary palace at Po Preah Bat, opposite of Phnom Penh on the Bassac River. Ang Chan also promoted his meritorious commanders Chakrey Long and Yomreach Hu to the positions of Chauvea Tolaha (Prime Minister) and Samdech Chauponhea (Deputy Prime Minister), respectively.