The Burmese–Siamese War (1785–1786), known as the Nine Armies' Wars (Thai: สงครามเก้าทัพ) in Siamese history because the Burmese came in nine armies, was the first war between the Konbaung dynasty of Burma and the Siamese Rattanakosin Kingdom of the Chakri dynasty.
King Bodawpaya of Burma pursued an ambitious campaign to expand his dominions into Siam. In 1785, three years after the foundation of Bangkok as the new royal seat and the Chakri dynasty, King Bodawpaya of Burma marched massive armies with total number of 144,000 to invade Siam in nine armies through five directions including Kanchanaburi, Ratchaburi, Lanna, Tak, Thalang (Phuket), and the southern Malay Peninsula. However, the overstretched armies and provision shortages deemed the Burmese campaign failed. The Siamese under King Rama I and his younger brother Prince Maha Sura Singhanat successfully warded off Burmese invasions. By early 1786, the Burmese had largely retreated.
After the truce during the rainy season, King Bodawpaya resumed his campaign in late 1786. King Bodawpaya sent his son Prince Thado Minsaw to concentrate his forces on Kanchanaburi in only a single direction to invade Siam. The Siamese met the Burmese at Tha Dindaeng, hence the term "Tha Din Daeng campaign". The Burmese were again defeated and Siam managed to defend its western border. These two failed invasions ultimately turned out to be the last full-scale invasion of Siam by Burma.
Background
Traditional rivalries and dispute over Mon rebels and the Tenasserim coast led to the Burmese-Siamese wars in the eighteenth century. In 1767, the Burmese of the newly founded Konbaung dynasty invaded and destroyed the Ayutthaya Kingdom. King Taksin of Thonburi reunited Siam in the aftermath of the destruction of the Ayutthaya government and capital. In 1774, most of the Lanna Kingdom, which had been under the Burmese rule for about 250 years, came under Siamese domination with exception of Chiang Saen still under Burmese rule. During the Burmese–Siamese War (1775–1776), Siam nearly succumbed to the Burmese forces led by General Maha Thiha Thura and Siam's manpower was depleted.
In 1782, Chao Phraya Chakri was crowned as the King Rama I of Siam and founded the Chakri dynasty. In the same year, Prince Badon Min dethroned King Phaungkaza Maung Maung and crowned himself as King Bodawpaya. King Bodawpaya began his reign with glorious military conquests. In 1784, he sent his son Prince Thado Minsaw to successfully conquer the Kingdom of Mrauk U or the Arakan Kingdom. After Arakan, King Bodawpaya turned his eyes on Siam as his next military expedition.
Nine Armies War (July 1785 – March 1786)
Burmese preparations
King Bodawpaya began his Siamese expeditions in July 1785. The Burmese forces were drafted from its various tributary states, most notably the northern Shan states of Hsenwi, Mongnai, Kengtung, Banmaw, Mongkawng and Hsipaw. Bodawpaya first sent Mingyi Mingaung Kyaw to lead an army of 10,000 men to Martaban to arrange the provisions and supplies for the massive royal army and for the fleets at Mergui. However, supply shortage and line communications were the main issue for the Burmese armies. The Burmese were unable to quickly move the large number of men and provisions in time.
King Bodawpaya and his armies left Ava on November 11, 1785. When the king arrived at Martaban on December 20, he found that the supplies did not meet the demands. He ordered Mingyi Mingaung Kyaw arrested from Mergui to be brought to him in chains. After waiting for four days at Martaban, King Bodawpaya was furious that the transportation of men, horses and elephants across the Salween River was delayed and had not been completed. He struck a spear at one of his generals, wounding him. Only with the beseeching of the governor of Kawthanti that the royal temper was cooled down. After staying in Martaban for a month, King Bodawpaya and his royal forces left Martaban on January 19, 1786, towards the Three Pagodas Pass.
Siamese preparations
In November 1785, three Burmese men were captured by the Karens of Kyaukkaung. The captured Burmese revealed to Siamese authorities that King Bodawpaya was planning a massive invasion of Siam in multiple directions. King Rama I convened a council of royal princes and ministers to discuss the situation. The Siamese then sent a Burmese man named Nga Gan, who was a former retainer of King Bodawpaya captured by the Siamese, to negotiate with King Bodawpaya at the Three Pagodas. King Bodawpaya, however, was not interested in peace-making and instead inquired Nga Gan about Siamese preparations. The Bangkok court then sent warnings to various cities in Northern and Southern Siam about the impending invasions.
Nine Armies War: Order of battle
From Martaban, Bodawpaya marched his armies through the Three Pagodas Pass. He ordered fourth and fifth divisions to enter through the Three Pagodas first into Kanchanaburi, followed by sixth and seventh divisions of his two sons and then the king's own army settled in Ranti (Alante) River. The vanguard of Minhla Kyawdin and Mingyi Maha Mingaung headed for the old city of Kanchanaburi (known today as "Latya", about fifteen kilometers to the northwest of modern city of Kanchanaburi), while the two princes stationed at Tha Dindaeng and Samsop in modern Sangkhlaburi District.
Kanchanaburi front
Prelude
In December 1785, Prince Maha Sura Singhanat, the Uparat (Viceroy) of Siam, led an army of 30,000 men out of the capital to confront the Burmese invasion. By royal decree, Phraya Kalahom Ratchasena and Phraya Chasaenyakorn were appointed to command the vanguard, while Chao Phraya Rattanapipit (Son) served as the kiakkai (camp marshal) and Prince Chakchetsada acted as the yokkabat (military auditor). The Siamese forces advanced to Tambon Lat Ya in Kanchanaburi, situated at the foot of the Banthat Range. There, the Prince ordered the army to establish a defensive position on the Lat Ya plain, featuring a camp with interconnected "wings" designed to maintain a continuous line of defense. Additionally, Binnya Sein (Phraya Mahayotha) was commanded to lead 3,000 Mon troops to intercept the Burmese at Dan Kram Chang, located in what is now Erawan National Park.
The main invasion force under King Bodawpaya entered Kanchanaburi through the Three Pagodas Pass. The 4th Burmese column, led by Myin Wun, advanced via Sai Yok and crossed the Khwae Yai River at Tha Kradan. Following the river downstream to Dan Kram Chang, Myin Wun's 10,000-man force routed the Mon contingent under Phraya Mahayotha and subsequently established a camp at Lat Ya. This force was later bolstered by the 5,000-man 5th column under Myinmawun, bringing the total Burmese strength at Lat Ya to 15,000 troops.
Other segments of the Burmese army were positioned strategically: the 6th column under Prince Thiri Damayaza at Tha Din Daeng; the 7th column under Prince Thado Minsaw at Sam Sop; and the 8th column—the main royal army of King Bodawpaya—at the Ranti River. The Siamese attempted to negotiate with Bodawpaya at the Ranti River by sending Nga Kan (or Na Khan), a captive from the War of Athi Wungyi, as an envoy, but the mission was unsuccessful. Despite their strategic positions, the Burmese forces suffered from severe logistical failures and provision shortages. The large host was unable to secure enough local supplies, and the difficulty of transporting provisions from distant regions significantly hampered the vanguard's operations.
Battle of Thung Lat Ya
Maha Sura Singhanat sent a Siamese army to attack the Burmese, but the Burmese were able to repel the Siamese attack. Both sides started building towers to place cannons on top to bomb each other. Both sides suffered heavy losses. To dissuade the Siamese soldiers from retreating, Maha Sura Singhanat built 3 large mortars and announce that if anyone retreats, they will be crushed by them.
Prince Maha Sura Singhanat noticed the Burmese supply lines were thin so he sent 500 men under the command of Phraya Siharatdecho, Phraya Tai Nam, and Phraya Phetchaburi to go ambush the Burmese supply lines at Phu Krai Sub-district. These men were too afraid to attack the Burmese army so they hid. They were later caught and beheaded. Maha Sura Singhanat then sent a force of 1,500 men under Khun Noen to ambush the Burmese supply lines. This devastated the Burmese supply lines.
A stalemate
The battle reached stalemate and was dragged on to January 1786. Being afraid that his brother would lose the engagement, King Rama I decided to march his 20,000-men army from Bangkok in January 1786 to support Maha Sura Singhanat Lat Ya, but the prince then convinced the king to return to Bangkok because he was confident of winning the engagement.
Breaking the stalemate
The Burmese side, upon observing the royal army arriving from Bangkok, believed that the Siamese was being reinforced. Prince Maha Sura Singhanat then had his army secretly march out of Lat Ya at night and march into Lat Ya again in the day, tricking the Burmese into believing that the Siamese was reinforced. With supply lines disrupted, the Burmese at Lat Ya were starved and deprived of morale. The Burmese killed horses for meat and dug for plant roots to eat. On 18 February 1786, the Siamese staged the all-out attack against the Burmese lines. Minhla Kyawdin and Mingyi Maha Mingaung the Burmese generals, unable to withstand Siamese attacks anymore, retreat. King Bodawpaya decided to give up the campaigns and ordered the general retreat of the Burmese armies on February 21, 1786.
Aftermath
After two months of battle, the Siamese were able to repel the Burmese invasion at Lat Ya. Prince Maha Sura Singhanat ordered the Siamese to follow the retreating Burmese as far as Sangkhlaburi where the armies of the two Burmese princes were stationed. Prince Thiri Damayaza and Prince Thado Minsaw reported to King Bodawpaya at Ranti River about the defeat. King Bodawpaya then ordered the general retreat. A large number of Burmese were captured as prisoners. Thai sources mentioned that the Burmese suffered around 6,000 casualties as a result of the battle.
Ratchaburi front
Prelude
Nemyo Nawrahta divided his 10,000-men army into 3 groups. Nemyo Nawrahta himself led an army of 4,000 men through the Bong Ti Pass (in modern Sai Yok District, Kanchanaburi Province) and stationed at Chom Bueng. Nemyo Nawrahta also sent his subordinate Dawei Wun to lead an army of 3,000 men to enter Ratchaburi through Suan Phueng. Dawei Wun and his army stayed at Khao Ngu, just five kilometers to the northwest of the town of Ratchaburi itself. They sustained themselves by harvesting coconuts and other fruits in the region. The remaining 3,000 troops were sent to join the 1st Division under Maha Thiri Thihathu at Myeik. Chao Phraya Thamma Boonrot, who led the Siamese army of 5,000 men in Ratchaburi town, was still unaware of these Burmese advances.
Battle of Khao Ngu
After defeating the Burmese at Lat Ya in February 1786, Prince Maha Sura Singhanat then marched to Ratchaburi. He sent his two generals Phraya Kalahom Ratchasena and Phraya Chasaenyakorn ahead as vanguard. The two generals met the Burmese at Khao Ngu and defeated Dawei Wun and the Burmese army in the Battle of Khao Ngu. Dawei Wun retreated towards Suan Phueng and was followed by the Siamese. Nemyo Nawrahta at Chom Bueng, upon seeing the defeat of Dawei Wun at Khao Ngu, also decided to retreat as soon as he had received orders from King Bodawpaya.
Aftermath
Prince Maha Sura Singhanat was angry that the Siamese general Chao Phraya Thamma Boonrot had allowed the Burmese to penetrate so deep into Ratchaburi. The prince petitioned King Rama I for Thamma Boonrot to be executed. However, as Thamma Boonrot had been a supporter in his ascension, King Rama I ordered his life to be spared. Thamma Boonrot was then whipped and paraded through the camps in shame with his head shaved. He was also stripped of his title and position as the Minister of Palatial Affairs.
Northern front
Siege of Lampang
Prince Thado Thiri Maha Uzana ventured to recruit men from the Shan States and marched the Burmese army of 30,000 men to Chiang Saen. The Burmese governor of Chiang Saen called Aprakamani also provided resources. As Chiang Mai had been abandoned since 1776, the main outpost of the Lanna Kingdom against the Burmese was Lampang. Prince Thado Thiri Maha Uzana and Aprakamani marched from Chiang Saen to attack Lampang in December 1785, leading to the siege of Lampang. Prince Kawila, the ruler of Lampang, defended the city.
Preludes to the Battle of Pakphing
Prince Thado Thiri Maha Uzana also sent his Sitke, Nemyo Sithu, to lead an army of 3,000 from Lampang down south towards the Upper Chao Phraya Plains. The governors of Sawankhalok, Sukhothai and Phitsanulok, due to manpower shortages, decided to abandon their cities and flee into the jungles as they were unable to raise armies against the Burmese. Nemyo Sithu marched through these cities unopposed and stationed his camps at Pakping, twenty kilometers to the south of the city of Phitsanulok. The 9th Division of Nawrahta Kyawgaung also entered the Chao Phraya Plains from the west through Rahaeng or modern Tak. The governor of Tak surrendered and was captured to Burma.