The Burmese–Siamese War (1775–1776) or Maha Thiha Thura's Invasion of Siam or Athi Wungyi's War (Thai: สงครามอะแซหวุ่นกี้) was a major military conflict between the Konbaung dynasty of Burma (now Myanmar) and the Thonburi Kingdom of Siam (now Thailand).
After the Mon Rebellion of 1774 and the successful Siamese capture of Burmese-held Chiang Mai in 1775, King Hsinbyushin assigned Maha Thiha Thura the general of Sino-Burmese War to conduct a large-scale invasion of Northern Siam in late 1775 in order to curb the rising Siamese power under King Taksin of Thonburi. As the Burmese forces outnumbered the Siamese, the three-month siege of Phitsanulok was the main battle of the war. Defenders of Phitsanulok, led by Chaophraya Chakri and Chaophraya Surasi, resisted the Burmese. The war reached stalemate until Maha Thiha Thura decided to disrupt the Siamese supply line, leading to the Fall of Phitsanulok in March 1776. The Burmese gained upper hand but the untimely demise of King Hsinbyushin ruined the Burmese operations as the new Burmese king ordered the withdrawal of all troops back to Ava. The premature exit of Maha Thiha Thura from war in 1776 left the remaining Burmese troops in Siam to retreat in disarray. King Taksin then took this opportunity to send his generals to harass the retreating Burmese. The Burmese forces had completely left Siam by September 1776 and the war was over.
The Maha Thiha Thira's Invasion of Siam in 1775–1776 was the largest Burmese-Siamese war in the Thonburi Period. The war (and subsequent wars) entirely wrecked and depopulated large sections of Siam for decades to come, some regions would not be entirely repopulated until the late 19th century.
Background
Reunification of Siam
After the fall of the Burmese Toungoo dynasty at the hands of the Mons of the Restored Hanthawaddy Kingdom in 1752, the new Burmese Konbaung dynasty emerged powerful. King Hsinbyushin of Burma was determined to accomplish the unfinished campaign of his father Alaungpaya to conquer Siam. He sent Nemyo Thihapate to pacify Lanna in 1764 and to proceed to conquer Ayutthaya and also sent another general Maha Nawrahta to lead Burmese troops from Tavoy to attack Ayutthaya, imposing two-pronged pincer attack onto Ayutthaya. Burmese Tavoy column under Maha Nawrahta and the Burmese-Lanna column under Nemyo Thihapate converged on Ayutthaya in January 1766. Ayutthaya under Siamese king Ekkathat sent out forces in attempts to repel and dislodge Burmese besiegers at Ayutthayan outskirts but all failed. Phraya Tak, the governor of Tak of Teochew Chinese descent, with personal name Zheng Xin (鄭信) or Zheng Zhao (鄭昭), who had been called to defend Ayutthaya, was among the Siamese commanders. Phraya Tak and his comrade Phraya Phetchaburi Rueang the governor of Phetchaburi fought the Burmese regiment of Maha Nawrahta at Wat Phukahothong temple to the northwest of Ayutthaya citadel but were eventually outmaneuvered and defeated. Situation for Ayutthaya defenders became dire and worsened as the Burmese unexpectedly persisted in the rainy season, depleting Ayutthaya of manpower and resources. With his comrade Phraya Phetchaburi dying in battle in November 1766 and ineffective leadership under Siamese king Ekkathat, Phraya Tak became desperate and decided to leave Ayutthaya. In January 1767, about three months before the eventual fall of Ayutthaya, Phraya Tak gathered 500 Chinese–Siamese followers to break through Burmese encirclement to the east. Phraya Tak fought through Burmese forces and local Siamese resistances all the way from Ayutthaya down to Eastern Siam, encamping at Rayong in late January 1767.
It was in Rayong that Phraya Tak learned about the fall of Ayutthaya in April 1767. In June 1767, Phraya Tak moved to attack and conquer the rival regime of Chanthaburi. Phraya Tak spent about four months at Chanthaburi on Siamese Eastern coast gathering his army and building his ships. In October 1767, Phraya Tak set sail with his forces of 5,000 men from Chanthaburi to reconquer Ayutthaya. After the fall of Ayutthaya in April 1767, the Burmese conquerors under Nemyo Thihapate left Ayutthaya two months later in June because the ongoing Sino-Burmese War prompted Burma to divert most of its occupying forces in Ayutthaya to the Chinese front. Nemyo Thihapate left only a handful of men under Thugyi the Mon headman at Phosamton (modern Bang Pahan district) to the north of Ayutthaya to occupy Lower Central Siam but the rest of Siam was divided under many regional regimes. Phraya Tak, with his forces, prevailed over Thugyi in the Battle of Phosamton in November 1767 and reconquered Ayutthaya from the Burmese occupiers, seven months after the fall of Ayutthaya. Phraya Tak found that the royal city of Ayutthaya, the royal capital of Siam for four centuries, was in the state of ruins and could not be a tenable fortress against the prospective Burmese retaliation. In strategic move, Phraya Tak established his new Siamese capital at Thonburi to the south of Ayutthaya. Phraya Tak officially enthroned himself on 28 December 1767 as King Taksin, reestablishing Siam and founding the Thonburi kingdom.
Following the Sack of Ayutthaya in 1767, a power vacuum emerged in Siam, which was filled by the establishment of five separate Siamese regimes—Phimai, Phitsanulok, Sawangburi, Nakhon Si Thammarat, and Thonburi. The Siamese state of Thonburi, led by Taksin, formerly the governor of Tak Province in Siam, would ultimately prevail out of the four, subjugating its four rival states and reunifying Siam by 1771. The Burmese, meanwhile, were preoccupied in having to contend with four major Qing invasions of Burma in 1765–69, thereby delaying an effective response to the new Siamese king. Taksin, from his capital of Thonburi, repelled a Burmese incursion in the Battle of Bangkung in 1768.
Sino–Burmese War
Conflicts between Konbaung Burma and China under the Qing dynasty over the sovereignty over the frontier Tai-Shan polities including Hsenwi, Kengtung and Sipsongpanna led to the Sino-Burmese War. In retaliation for Burmese attack on Sipsongpanna, Liu Zhao (劉藻) the viceroy of Yungui led Chinese forces to attack Burmese-held Kengtung in 1765 but was repelled. Liu Zhao committed suicide in guilt and he was replaced by another viceroy Yang Yingju (楊應琚), who, from his base at Yongchang, sent Qing armies to directly invade Burma in October 1766 but faced tough resistance from the Burmese stockade of Kaungton, unable to proceed further. Qing invasions came in the same time when the Burmese forces were besieging Ayutthaya. Burma then had to conduct war on two fronts simultaneously; the Siamese and the Chinese fronts. Another Qing army attacked Theinni but was outflanked from the rear by Maha Thiha Thura from Sipsongpanna. As tropical malaria ravaged, Qing Chinese forces ended up being repelled and besieged in their own town of Longchuan. Covering up his defeats, Yang Yingju sent false reports to Emperor Qianlong but his lies were eventually exposed and Yang Yingju was called to Beijing to be forced to commit suicide as punishment.
Chinese invasions prompted Burmese king Hsinbyushin to call the Burmese contingents from Siam to the Chinese front. Suffering from humiliating defeats, Emperor Qianlong was determined to conquer Burma to uphold dignity. The emperor blamed Han Chinese Green Standard regiment for failures and began to employ Manchu bannermen in the Burmese campaign. Qianlong sent a Manchu general Mingrui (明瑞) as the new Yungui viceroy and leader of the campaign. Mingrui, with mixed Han-Manchu forces of 25,000 men, invaded Burma in November 1767, seizing Theinni and defeating the Burmese in the Battle of Goteik Gorge – the first major Qing victory (Meanwhile, Phraya Tak expelled the Burmese occupation forces from Ayutthaya in November 1767). Mingrui and his forces reached Singu, just thirty miles north of the Burmese royal capital of Ava but another Qing army intended to converge on Ava could not get through the formidable Kaungton fortress. It was during this time that the Burmese tactic of attacking and disrupting communication supply line came into play, becoming staple and crucial strategy for future Burmese successes. Maha Thiha Thura, with Burmese forces of 20,000 men, retook Theinni to sever the Qing supply line and to block the exit of the Qing army, entrapping the Qing forces starved inside of Burma. Mingrui and the Qing forces decided to retreat but suffered deadly defeats at the hands of the Burmese in the Battle of Maymyo and at Mongyu in March 1768, where many Qing commanders were killed. Mingrui himself cut his Manchu queue sending to the emperor as apology and hanged himself on a tree in suicide.
Not giving up, Qianlong appointed his brother-in-law and chief state councilor Fuheng (傅恆) to be the new leader of the Burmese campaign in April 1768. Fuheng devised a new strategy. He preferred the route down along the Irrawaddy River to directly attack Ava. In October 1769, having total of 40,000 men, Fuheng sent some Qing forces to seize control of Shan States of Mongkawng and Mongyang, gaining access to the Irrawaddy, constructing his fleet and establishing the Chinese fortress at Shwenyaungbin. Fuheng, however, was too slow as Hsinbyushin quickly sent the Burmese fleet of 12,000 men under Nemyo Sithu to destroy the newly-constructed Qing fleet at Mogaung and sent massive Burmese army of 52,000 men under Maha Thiha Thura to successfully take the Chinese Shwenyaungbin fortress. A Burmese regiment was specifically assigned to disrupt Chinese supply line. Eventually, the malaria overwhelmed the Chinese forces with many Qing commanders dying or falling ill. Fuheng himself was incapacitated by the illness and relegated his duty to his deputy Agui (阿桂). Agui preferred peace and opened negotiation with Maha Thiha Thura. Without approval from the Burmese king, Maha Thiha Thura reached an agreement with Agui on 22 December 1769 in the Treaty of Kaungton, with the Qing promising to recognize Burmese sovereignty over the disputed Shan princedoms in exchange for Burma sending elusive amicable 'tributary' missions to Beijing. (In the same time, King Taksin was conquering the Southern Siamese regional regime of Chao Nakhon Nu in late 1769.) Fuheng died from illness shortly after.
The Treaty of Kaungton practically ended the Sino–Burmese War but Burmese king Hsinbyushin, enraged, did not accept this agreement. Facing the wrath of his overlord, Maha Thiha Thura led the Burmese forces to attack Manipur in early 1770 to appease the Burmese king. As Burma did not actually send those said missions to China, Emperor Qianlong ordered the shutdown of the Sino–Burmese borders, disrupting the trade at the expense of local Chinese and Shan merchants. Burma and China remained technically at war for two decades until 1788 when, through manipulation of the Shans who wanted the Sino–Burmese trade to resume, King Bodawpaya of Burma sent a diplomatic mission to Beijing. Qianlong finally consented to Burmese sovereignty over the disputed Shan States and lifted the trade embargo at the border.
Resumption of Burmese–Siamese conflicts
Despite the Fall of Ayutthaya and the total destruction of the Siamese Kingdom in 1767, the Siamese had recovered and consolidated under the leadership of Phraya Tak or King Taksin. After peace was officially concluded between Konbaung Burma and Qing China, the Burmese king was eager to subjugate the newly rising rival Siamese power. Hsinbyushin ordered Nemyo Thihapate to gather troops at Lanna Chiang Mai and appointed Mingyi Kamani Sanda as the new governor of Martaban to organize forces to invade Siam in 1772. Hsinbyushin intended to inflict the pincer attack on Siam both from the north and from the west, in similar manner to the Burmese invasion of 1765–67.
At this time, the Burmese military command had broken down. Dissension was rampant. Field commanders increasingly acted like warlords and behaved with arrogance towards the people, and began to ignore even the king's orders which created rebellions by their otherwise loyal leaders. In 1774, Mingyi Kamani Sanda the governor of Martaban ordered the Mon regiment under the command of Mon leaders including Binnya Sein (a nephew of Binnya Dala, the former king of Hanthawaddy Kingdom), to lead the vanguard army to invade Siam through the Three Pagodas Pass. Once the Mon leaders had left Martaban, however, Mingyi Kamani Sanda forcibly extorted money and wealth from the Mon families and inhabitants of Martaban to fund the campaigns. News reached Binnya Sein and other Mon leaders about the Burmese mistreatments in their absences. The Mon leaders were then enraged that, despite their contributions to the Burmese cause, their fellows and families behind were unjustly abused. Binnya Sein and other Mon leaders mutinied and marched back to seize Martaban. Mingyi Kamani Sanda fled and took refuge at Yangon. The Mon forces continued marching and managed to temporarily take control of Yangon but were eventually repelled by the Burmese rescue armies. Defeated, Binnya Sein took safety shelter in Siam. Great number of Mon people from Martaban also went on the mass exodus into Siam through the Mae Lamao Pass and the Three Pagodas Pass to escape the punishing hands of their Burmese overseers. In 1774, King Hsinbyushin assigned Wungyi Maha Thiha Thura, the renown general from the Sino-Burmese War, called Athi Wungyi (Thai: อะแซหวุ่นกี้) in Thai sources, to lead the Burmese troops of 35,000 men to Martaban to capture the Mons and to invade Siam.