2377), Vietnamese: Chiến tranh Việt–Xiêm (1833–1834)), also known as the Siamese-Cambodian War of 1831–1834, was sparked by a Siamese invasion force under General Bodindecha that was attempting to conquer Cambodia and southern Vietnam.

After initial success and the defeat of the Khmer Army at the Battle of Kompong Cham in 1832, the Siamese advance was repelled in southern Vietnam in 1833 by the military forces of the Nguyễn dynasty.

In the seventeenth century, Vietnam, led by the Nguyen Lords of Đàng Trong, expanded to the south into Mekong delta of Cochinchina, which had been Cambodian territories, in the process known as Nam tiến.

Dynastic factional conflicts in Cambodia aggravated the issue[6] as rival princely candidates usually sought supports from either Siam or Vietnam in their claims to Cambodian throne.

Another turn of event occurred in 1778 when Chauvea Tolaha Mou, the Cambodian Prime Minister, rebelled against Ang Non with support from the Nguyen Lord Nguyễn Phúc Ánh, who was fighting the Tây Sơn at the same time.

[8] Defeated, Nguyễn Phúc Ánh took refuge in Bangkok[8] where he was well-received by the Siamese court, partly due to the preceding peace negotiations in Cambodia in 1782.

Also in 1809, the Burmese invaded Phuket and King Rama II asked for Ang Chan to contribute forces as vassal kingdoms were expected to provide military assistance.

Panicked, King Ang Chan, escorted by Nguyễn Văn Thoại, fled from Oudong to take refuge at Saigon where he was accommodated by the Vietnamese.

In 1813, Gia Long assigned Lê Văn Duyệt, who had just been appointed as the governor of Saigon in 1812,[14] to lead the Vietnamese army of 13,000 men[6] to escort Ang Chan back to Cambodia with Siamese representatives as witnesses.

Ang Chan chose to reside at Phnom Penh rather than Oudong owing to its riverside position being accessible to Vietnamese protection navy.

Lê Văn Duyệt (called Ong Ta Kun in Thai and Cambodian chronicles) was appointed as Gia Định Thành[14] or governor of Saigon citadel in 1812, which acted as the viceroy of Cochinchina or Southern Vietnam and also had authorities over Cambodia.

[6] Lê Văn Duyệt also built a Vietnamese shrine for Emperor Gia Long at Chroy Changvar, the land opposite of Phnom Penh on the river.

In 1815, at suggestion of Nguyễn Văn Thoại,[13] Ang Chan sent Cambodian forces led by Samdech Chauponhea Tey[13] to attack Battambang and reclaim Northwestern Cambodia from Siam.

[15] Nguyễn Văn Thoại was put in charge of the project with dedicative participation from King Ang Chan of Cambodia as Cambodian people were conscripted to labor works on the canal supervised by the Vietnamese.

Minh Mạng initially maintained neutral attitude towards Siam and also took cautious approach on his powerful mandarin Lê Văn Duyệt, who was appointed as the governor of Saigon for the second time, in the same year.

In 1824, King Rama II of Siam died and Anouvong traveled to Bangkok to attend the royal funeral but faced derogatory treatment.

[20] Warlord Lê Văn Duyệt held the position of Gia Định Thành or governor of Saigon from 1820 to his death in 1832[22] and, during his tenure, had been the most powerful minister of Southern Vietnam, also holding influence over Cambodia.

Under his rule, Lê Văn Duyệt allowed Chinese immigrants to flourish in their trades and Christian Southern Vietnamese to enjoy their religious freedom.

Minh Mạng considered Southern Vietnam to be an unruly autonomous region where illegal opium imports by Chinese immigrants and Christianity were allowed and tolerated.

[24] Bạch Xuân Nguyên reported to Minh Mạng at Huế that the recently-deceased Lê Văn Duyệt had been corrupted and abusive of his powers.

The rebels murdered Minh Mạng's officials including Nguyễn Văn Quế and Bạch Xuân Nguyên the governors of Saigon.

Tống Phước Lương was successful against the rebels, reconquering all of Southern Vietnam for Minh Mạng by late 1833 except for the Saigon citadel itself where Lê Văn Khôi stood.

Pro-Siamese Cambodian figures, including Preah Angkeo Ma and Oknha Kas the former governor of Pursat,[13] who had been taking refuge in Siam, also joined the main Siamese land division under Chaophraya Bodindecha.

The main column of Chao Phraya Bodindecha, led by shock troops with a great number of war elephants,[2] marched from Battambang to seize Pursat and Kampong Chhnang.

Phraklang then retreated further to Hà Tiên through the Vĩnh Tế Canal and carried off the local population of Banteai Meas, Kampot, and Kampong Som to be resettled in Chanthaburi.

However, revolts against the Siamese invaders broke out in Phnom Penh and the rest of Cambodia under the co-ordinated leadership of two Khmer magistrates, Chakrey Long and Yumreach.

[1] Vietnamese and Cambodian forces under Nguyễn Xuân, Lê Đại Cương, Trương Minh Giảng and Chakrey Long pursued the retreating Siamese deep into Cambodia.

Vietnamese forces in Muang Phuan was left unsupported as Tạ Quang Cự the governor of the adjacent Nghệ An and Hà Tĩnh provinces was sent away to suppress the rebellion of Nông Văn Vân in the same year.

[14] Nguyễn Xuân, the leading Vietnamese general who defeated both the Siamese and the rebels, died in late 1835, leaving Trương Minh Giảng as the main meritorious powerful official in Southern Vietnam.

He arrested Siamese officials in Battambang and, along with its inhabitants, deported them to join Trương Minh Giảng at Phnom Penh in hope that Vietnam would make him King of Cambodia.