Siamese–Vietnamese War (1831–1834)


The Siamese-Vietnamese War of 1831–1834, Chiến tranh Việt–Xiêm ), also known as the Siamese-Cambodian War of 1831–1834, was sparked by a Siamese invasion force under general Bodindecha, attempting to conquer Cambodia and Southern Vietnam. After initial success and the defeat of the Khmer army at the 1832 Battle of Kompong Cham, in 1833 the Siamese advance was repelled in South Vietnam by the forces of the Nguyen Dynasty. Upon the outbreak of a general uprising in Cambodia the Siamese army withdrew and Vietnam was left in control of Cambodia.

Background

ฺBoth Siam and Vietnam emerged as the primary powers in Indochina by the early nineteenth century and increasingly sought to dominate Cambodia and Laos in their effort to gain hegemony over the Lower Mekong Basin. The internal struggles between factions of Cambodian royal families during the Cambodian Dark Ages, Siam and Vietnam aggressively intervened on opposite sides to maximize their influences over Cambodia. They adopted the tradition to take members of the Cambodian royal family hostage, interfered in marriage policies, influenced and orchestrated their protégées and demanded loyalty.
In 1806 Ang Chan II was crowned King of Cambodia by the Siamese, who however would eventually become pro-Vietnamese. He did not attend the funeral of the Siamese King Rama I in 1809 and sent his younger brothers Prince Ang Snguon and Prince Ang Em to Bangkok in his stead. King Rama II then made Prince Ang Snguon the Uprayorach - vice-king and Prince Ang Em the Ouparach - deputy vice-king, thus placing the two princes under Siamese overlordship. Just two years later, in 1811, Prince Ang Sngoun rebelled against his brother the king, that lead to a nation-wide rebellion. King Rama II then sent Chao Phraya Yommaraj Noi to lead an army to Oudong and settle the issues. Upon the arrival of a Siamese army, King Ang Chan fled to Saigon under the protection of Lê Văn Duyệt, the viceroy of Cochinchina. Prince Ang Em and Ang Duong, the younger brothers of King Ang Chan, also joined the Siamese side. Emperor Gia Long of Vietnam negotiated with King Rama II to restore King Ang Chan to the throne so King Rama II ordered Chao Phraya Yommaraj Noi to return, taking with him the three princes Ang Sngoun, Ang Em and Ang Duong. Lê Văn Duyệt had King Ang Chan restored back at Phnom Penh. Cambodia had thus moved towards Vietnamese domination. Prince Ang Sngoun died at Bangkok in 1816 leaving only the younger brothers Prince Ang Em and Ang Duong.
After his initial defeat in the Lao rebellion in 1827, King Anouvong of Vientiane fled to the Nghệ An Province in Vietnam. Emperor Minh Mạng accommodated the Lao king and sent his envoys to bring King Anouvong back to Vientiane to negotiate with the Siamese. However, Anouvong later ambushed the Siamese garrisons at Vientiane and Siam was convinced that Vietnam supported King Anouvong in his resistance to Siamese domination. When Anouvong was defeated again in 1828 and fled to Xiangkhouang, Chao Noy the ruler of Muang Phuan, who was a former vassal to Anouvong and then later became a vassal of Vietnam, revealed the whereabouts of Anouvong to Chao Phraya Bodindecha that led to the capture of Anouvong. Emperor Minh Mạng then summoned Chao Noy to Huế and had him executed. Emperor Minh Mạng later annexed the Kingdom of Muang Phuan into Vietnamese direct rule, becoming the province of Trấn Ninh.
Lê Văn Duyệt had been a powerful mandarin of Southern Vietnam and exerted his influence over Cambodia. After his death in 1832, Emperor Minh Mạng condemned Lê Văn Duyệt to the charge of treason and prosecuted his associates. Lê Văn Khôi, adoptive son of Lê Văn Duyệt, led the Lê Văn Khôi revolt in May 1833 and took Saigon. King Rama III then took this opportunity to dismantle the Vietnamese influences in Cambodia and in the region. King Rama III initiated the Siamese campaign to bring Prince Ang Em to the Cambodian throne and to take Saigon.

Siamese preparations

King Rama III arranged the Siamese forces into the following routes;

Siamese Invasion of Cambodia, Hà Tiên and An Giang

All three Siamese armies left Bangkok on the same day in November 1832. King Ang Chan and his court immediately fled to Long Hồ in Vĩnh Long Province. The main column of Chao Phraya Bodindecha marched from Battambang on the eastern bank of the Tonle sap lake to seize Pursat and Kampong Chhnang. The second column advanced on the western bank of the lake. Bodindecha left the princes Ang Em and Ang Duong at Phnom Penh and proceeded to Ba Phnum. The fleet of Phraklang reached Hà Tiên in January 1833. The Vietnamese, who had been preoccupied with Lê Văn Khôi's rebellion, were caught unprepared and the Siamese quickly took Hà Tiên. Phraklang then sailed his fleet upstream the Vĩnh Tế Canal and also quickly took Châu Đốc in the An Giang Province. Bodindecha, who had reached Ba Phnum, sent his brother-in-law Chao Phraya Nakhon Ratchasima to bring 7,000 men eastwards through Ba Phnum district directly to Saigon and Bodindecha himself joined Phraklang at Châu Đốc. Emperor Minh Mạng then ordered Trương Minh Giảng and Nguyễn Xuân to counter the Siamese offensives in An Giang.

Battle of Vàm Nao

In order to reach Saigon from Châu Đốc, the Siamese fleet had to cross from the Bassac River to the Mekong via the Vàm Nao Canal. Chao Phraya Bodindecha merged his army into Phraklang's fleet and the massive Siamese fleet proceeded along the Bassac River, reaching the Vàm Nao Canal or Thuận Cảng Canal in January 1833 where they met the Vietnamese fleet. The Battle of Vàm Nao ensued. The Siamese initially prevailed. The Vietnamese retreated towards the Mekong and the Siamese pressed on the attack. Bodindecha ordered his fleet to disembark and attack the Vietnamese on land but was repelled by the Vietnamese General Phạm Hữu Tâm. The admirals of Phraklang's fleet, however, refused to engage with the Vietnamese fleet. Phraklang himself had to board a small boat to encourage his admirals to attack but to no avail. Then Vietnamese reinforcements, including more than a hundred battle-junks led by Tống Phước Lương arrived and the overwhelming numbers of the Vietnamese engaged Bodindecha's armies. The Siamese were unable to withstand the Vietnamese and both Bodindecha and Phraklang decided to retreat in February 1834.

Siamese retreat and Vietnamese offensives

After the Battle of Vàm Nao, the Siamese retreated to Châu Đốc in January 1833. Trương Minh Giảng capitalized on the victory by sending a fleet to follow the Siamese and attack Châu Đốc. Chao Phraya Bodindecha ordered the Siamese to fire upon the disembarking Vietnamese resulting in bodies piling on the river bank. 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 Chanbury. The water of the Vĩnh Tế Canal was too shallow for the galleys to proceed. Phraklang then ordered some of the galleys to be pulled by elephants to Kampot. However, the Cambodians revolted and murdered the mahouts, taking all the elephants. As the Vietnamese kept attacking Châu Đốc, Bodindecha decided to abandon Châu Đốc and retreat from Cambodia to Chantaburi and take along as much of the local population as he could find on the way back.
Trương Minh Giảng reconquered Châu Đốc and Hà Tiên. Bodindecha instructed the princes Ang Em and Ang Duong at Phnom Penh to destroy the citadel, burn the city and march all inhabitants to Battambang. However, revolts against the Siamese invaders broke out in Phnom Penh and all over Cambodia and under the coordinated leadership of two Khmer magistrates, Chakrey Long and Yumreach all further Siamese hostile acts met massive resistance.. Bodindecha and the two princes then retreated towards Siam.
Chao Phraya Nakhon Ratchasima and Phraya Rachanikul, who had led the Siamese troops from Ba Phnum eastward to Saigon, were attacked by Cambodian insurgents and realized that the main Siamese forces had already retreated. They returned to the Mekong but found that all boats to cross the river had vanished and instead built a pontoon bridge to cross. Internal dissent caused some contingent commanders to leave the army group and marched northwards along the Mekong were they were massacred. Chao Phraya Nakhon Ratchasima and Phraya Rachanikul eventually crossed the Mekong and engaged the Cambodian insurgents. Chao Phraya Bodindecha ordered Chao Phraya Nakhon Ratchasima and Phraya Rachanikul to retreat to Nakhon Ratchasima. In 1834, viceroy Trương Minh Giảng and his vassal king Ang Chan returned to Phnom Penh and Vietnamese rule in Cambodia was established.

Xiangkhouang and Khammouane Fronts

Phra Mahathep and Phra Rachawarin reached their respective destinations in January 1833. Phra Mahathep stationed at Nakhon Phanom and Phra Rachawarin at Nongkhai. Phra Mahathep led Siamese army to attack the Phu Thai communities of modern Khammouane Province including Mahaxay, Muang Pong, Muang Plaan and Muang Chumporn, which had been under Vietnamese rule. The Siamese relocated the Phu Thai people to settle in modern Nakhon Phanom Province and surrounding areas.
After the execution of Chao Noy of Muang Phuan at Huế, Emperor Minh Mạng appointed a new ruler to Muang Phuan in 1833. Phra Rachawarin and Phra Patumthewa the governor of Nongkhai sent messages to the ruler of Muang Phuan to defect to the Siamese side. The ruler of Muang Phuan decided to join the Siamese cause and Phra Rachawarin led the Siamese army to capture Muang Phuan, defeating the Vietnamese forces. Muang Phuan as a tributary state to Siam was too far from Siamese influences and hard to defend. Siam then decided to dissolve the Kingdom of Muang Phuan altogether. Nearly all Phuan people of Muang Phuan were forcibly relocated to Nan, Sukhothai, Uttaradit and Phitsanulok provinces and Muang Phuan was left largely deserted.

Aftermath and Prelude to 1841-45 war

On 19 February 1833, American diplomat Edmund Roberts arrived at the Siamese port of Pak Nam simultaneously with an embassy from Vietnam. Roberts was only vaguely aware of the war, but soon learned the object of mission:
"...no less than to demand the delivery, to them, of the person of the first minister of state, and superintendent of Pegu, and the principalities of Laus and Camboja, whose title is "Chan-phaya-bodin-desha;" he is a "meh-tap," or commander of the Siamese forces now in Camboja."
This was a renewed demand arising from an incident during the Laotian Rebellion of 1826–1828. Minh Mang had sent an envoy with a hundred men to learn of Siamese intentions; which Bodindecha made known by leaving only one of them alive to return. The 1833 mission was coldly received, in sharp contrast with the attention given that of Roberts.