Burmese – Siamese War ( 1765 – 67 ) The Burmese – Siamese War ( 1765 – 1767 ) ( ; , lit . " war of the second fall of Ayutthaya " ) was the second military conflict between the Konbaung Dynasty of Burma ( Myanmar ) and the Ban Phlu Luang Dynasty of Siam ( Thailand ) , and the war that ended the four - century - old Siamese kingdom . Nonetheless , the Burmese were soon forced to give up their hard - won gains when the Chinese invasions of their homeland forced a complete withdrawal by the end of 1767 . A new Siamese dynasty , to which the current Thai monarchy traces its origins , emerged to reunify Siam by 1770 . This war was the continuation of the war of 1759 – 1760 . The casus belli of this war were also the control of the Tenasserim coast and its trade , and the Siamese support for the rebels in the Burmese border regions . The war began in August 1765 when a 20 , 000 - strong northern Burmese army invaded northern Siam , and was joined in by three southern armies of over 20 , 000 in October , in a pincer movement on Ayutthaya . By late January 1766 , the Burmese armies had overcome numerically superior but poorly coordinated Siamese defences , and converged before the Siamese capital . The siege of Ayutthaya began during the first Chinese invasion of Burma . The Siamese believed that if they could hold out until the rainy season , the seasonal flooding of the Ayutthayan central plain would force a retreat . But King Hsinbyushin of Burma believed that the Chinese war was a minor border dispute , and decided to continue the siege . During the rainy season of 1766 ( June – October ) , the battle moved to the waters of the flooded plain but failed to change the status quo . When the dry season came , the Chinese launched a much larger invasion but Hsinbyushin still refused to recall the troops . In March 1767 , King Ekkathat of Siam offered to become a tributary but the Burmese demanded an unconditional surrender . On 7 April 1767 , the Burmese sacked the starving city for the second time in history , committing atrocities that have left a major black mark on Burmese - Thai relations to the present day . Thousands of Siamese captives were relocated to Burma . The Burmese occupation was short - lived . In November 1767 , the Chinese again invaded with their largest force yet , finally convincing Hsinbyushin to withdraw his forces from Siam . In the ensuing Siamese civil war , Taksin ' s Thonburi forces emerged the sole winner by mid - 1770 . The Burmese had also defeated a fourth Chinese invasion by December 1769 . By then , a new stalemate had taken hold . Burma had annexed the lower Tenasserim coast but again failed to eliminate Siam as the sponsor of rebellions in her eastern and southern borderlands . In the following years , Hsinbyushin was preoccupied by the Chinese threat , and did not renew the Siamese war until 1775 — only after Lan Na had revolted again with Siamese support . The post - Ayutthaya Siamese leadership proved more than capable ; they defeated the next two invasions ( 1775 – 1776 and 1785 – 1786 ) , and annexed Lan Na in the process . Background . This war was the continuation of the war of 1759 – 1760 , the " casus belli " of which were over the control of the Tenasserim coast and its trade , and the Siamese support for ethnic Mon rebels of the fallen Restored Hanthawaddy Kingdom of Lower Burma . The 1760 war , which claimed the life of the dynasty founder King Alaungpaya , was inconclusive . Although Burma regained control of the upper Tenasserim coast to Tavoy ( Dawei ) , it achieved none of its other objectives . Following the war , the new Burmese king Naungdawgyi was beset with rebellions in Ava and Toungoo , and instabilities spread to the border regions . Lan Na ( Chiang Mai ) was in open rebellion ( 1761 – 1763 ) with active Siamese support . ( Siam even sent an army in support of the rebels . However , the Siamese chronicles claim that the army did not engage in the fighting because the Burmese army had already defeated the rebellion . ) In the Burmese south too , the Siamese readily provided shelter to the defeated ethnic Mon rebels who had raised an unsuccessful rebellion in 1762 . Things calmed down for a moment after the Lan Na rebellion was suppressed in January 1763 . Naungdawgyi , who had been putting down multiple rebellions since his accession , was eager to lead a peaceful reign . He chose not to renew a war with Siam despite Siam ' s active support of the Lan Na rebellion and continued sheltering of Mon rebels . But Naundawgyi died in November 1763 , and was succeeded by his brother Hsinbyushin who had wanted to continue the war with Siam since the end of the last war . The Siamese leadership was alarmed by Hsinbyushin ' s accession . Knowing that another war was inevitable , the Siamese leadership accelerated their policy of keeping Burmese regions unstable . In mid - 1764 , the Siamese successfully encouraged the ethnic Mon governor of Tavoy , who was appointed by Alaungpaya only four years earlier , to switch sides . Hsinbyushin was forced to send an army led by Maha Nawrahta , who retook Tavoy in November 1764 . Likewise , instabilities resumed in Lan Na right after the Burmese army left in February 1764 , forcing the Burmese to return to the region later in the year . By January 1765 , the Burmese armies were massed at Tavoy in the south and Chiang Mai in the north , preparing for the next war . Prelude to war . Burmese preparations . As the deputy commander - in - chief in the 1760 war , Hsinbyushin used his firsthand experience to plan the next invasion . His general plan called for a pincer movement on the Siamese capital from the north and the south . He appointed two of the country ' s most decorated soldiers Maha Nawrahta and Ne Myo Thihapate to lead the invasion . On the southern front , he kept Maha Nawrahta and his 20 , 000 strong army , who had just put down the Tavoy rebellion , at Tavoy . Their control of Tavoy now gave the Burmese the shortest route towards Ayutthaya . In the north , he sent Ne Myo Thihapate to raise an army from the Shan States throughout 1764 . By November , Ne Myo Thihapate commanded a 20 , 000 - strong army at Kengtung , preparing to leave for Chiang Mai . As customary , the Shan regiments were led by their own saophas ( chiefs ) . ( Not everyone was happy about the Burmese army ' s conscription drive , however . Some of the saophas of northern Shan states , which at the time paid dual tribute to Burma and China , fled to China , and complained to the Chinese emperor . ) The next step in Hsinbyushin ' s plan was to outflank the Siamese in their north and northeast . He ordered Ne Myo Thihapate to acquire the Laotian states of Vientiane and Luang Phrabang . Vientiane was acquired without a fight in January 1765 . Luang Phrabang put up a fight but was defeated in March 1765 . The defeated Laotian states then were forced to provide levies to the northern army . The entire northern Burmese command now had over 20 , 000 men . On 29 April 1765 , a northern invasion army of 20 , 000 was posted at Lampang at the Siamese border . ( The rest were assigned to garrisons in Kengtung and Chiang Mai to guard the rear . The precaution proved prescient as the Kengtung garrison successfully resisted the Chinese invasion of 1765 – 1766 . ) While the main Burmese armies were massed at the Siamese border , a rebellion broke out in Manipur . Characteristically , Hsinbyushin did not recall the armies . Instead , he personally led an expedition force to put down the rebellion himself in December 1764 . Having arrived back at Ava in April 1765 , the Burmese king then sent 10 , 000 men to reinforce the southern army , which now numbered 30 , 000 . The Burmese army now had mobilised 50 , 000 men . ( This likely represented the largest mobilisation of the Burmese army since Bayinnaung ' s 1568 – 1569 invasion . ) The Burmese artillery corps were led by a group of about 200 French soldiers who were captured in the battle of Syriam in 1756 during the Burmese civil war of 1752 – 1757 . Siamese preparations . The Siamese too had been busy planning their defences since Hsinbyushin accession . Their defences had been on alert since they got the Tavoy governor to revolt in mid - 1764 . King Ekkathat had already launched a massive mobilisation drive across the entire country when Maha Nawrahta came down with his army and retook Tavoy in November 1764 . In all , the Siamese southern defences alone comprised over 60 , 000 troops . Ekkathat placed several of " his best legions " along the entire western arc from the Three Pagodas Pass to Kanchanaburi across Tavoy , to the Gulf of Siam in the extreme south to face off Maha Nawrahta . In the north , the main Siamese defensive line began at Sukhothai and Phitsanulok . The defences farther north immediately facing the northern Burmese army relied on small forts built by local chiefs . Finally , the Siamese relied on a heavily fortified Ayutthaya city , strategically situated at the estuary of two rivers where high rising waters in the rainy season had kept it safe against enemies over the centuries . The Siamese had used their wealth to acquire several thousand muskets and artillery . Some of the cannon were thirty feet ( 9 m ) long , and fired 100 - lb . ( 45 - kg . ) balls . " ( When the Burmese finally captured Ayutthaya in 1767 , they found over 10 , 000 brand new muskets and ammunition in the royal armoury , still left unused even after a 14 - month siege . ) " As was the case in 1760 , foreign mercenaries ( including some Europeans and the Chinese ) were hired for Ayutthaya ' s defence . At least one English ship was enlisted for her broadside s . Invasion . Burmese battle plan . The Burmese battle plan was greatly shaped by their experience in the 1759 – 1760 war . First , they would avoid a single pronged attack route along the narrow Gulf of Siam coastline , which they discovered , could easily be clogged up by more numerous Siamese forces . In 1760 , the Burmese were forced to spend nearly three months ( January – March ) to fight their way out of the coastline . This time , they planned a multi - pronged attack from all sides to stretch out the numerically superior Siamese defences . Secondly , they would start the invasion early to maximise the dry - season campaign period . In the previous war , Alaungpaya started the invasion too late ( in late December 1759 / early January 1760 ) . When the Burmese finally reached Ayutthaya in mid April , they only had a little over a month left before the rainy season to take the city . This time , they elected to begin the invasion at the height of the rainy season . By starting the invasion early , the Burmese hoped , their armies would be within a striking distance from Ayutthaya at the beginning of the dry season . Start of invasion . Northern front ( August 1765 ) . The invasion began on 23 August 1765 ( 8th waxing of Tawthalin 1127 ME ) at the height of the rainy season when the 20 , 000 strong northern Burmese army ( 20 regiments and three hundred war - boats ) invaded Siam down the Wang River . The southern armies stayed put . The reason for the earlier start of the northern army was that it was much farther away from Ayutthaya than its southern counterparts . Still the strategy did not work as planned . The northern army ' s advance was greatly slowed by the rainy weather and the " petty chiefs " who put up a fight , forcing Thihapate to storm town after town . Nonetheless , Thihapate fought his way down the Wang , finally taking Tak and Kamphaeng Phet by the end of the rainy season . Southern front ( October 1765 ) . In the mean time , Maha Nawrahta opened the southern front on 23 October 1765 ( 10th waxing of Tazaungmon 1127 ME ) in three directions . He had 20 , 000 to 30 , 000 under his command . " ( The Burmese sources say 30 , 000 men including 2000 horses and 200 elephants but GE Harvey gives the actual invasion force as 20 , 000 . At least part of the difference could be explained by the rearguard who stayed behind to defend the Tenasserim coast . ) " A small army invaded by the Three Pagodas Pass towards Suphanburi . Another small army invaded down the Tenasserim coast towards Mergui ( Myeik ) and Tenasserim ( Tanintharyi ) town . However , the main thrust of his attack was at Kanchanaburi . His 20 , 000 - strong main southern army invaded via the Myitta Pass . " ( It was also the same route the Japanese used in 1942 to invade Burma from Thailand . ) " Kanchanaburi fell with little resistance . The main reason for the quick fall of Kanchanaburi could be that the Burmese were more battle - hardened . But it could also be that the Siamese command miscalculated where the Burmese main attack would come from , and had not sufficiently reinforced the fort to withstand a major attack . Judging by the Siamese chronicles ' reporting of the main attack route , the Siamese command appeared to have believed that the main Burmese attack would come from the Gulf of Siam coastline , instead of the most obvious and shortest route via Kanchanaburi . The Siamese sources say that Maha Nawrahta ' s main invasion route came from southern Tenasserim , crossing the Tenasserim range at Chumphon and Phetburi . The path is totally different from the Kanchanaburi route reported by the Burmese chronicles . Historian Kyaw Thet specifically adds that the main attack route was via the Myitta Pass . First dry season offensive . Nonthaburi and western Ayutthaya ( November – December 1765 ) . After Kanchanaburi , Maha Nawrahta ' s southern army marched on towards south of Ayutthaya , and faced token opposition until they reached Nonthaburi about 60 km south of Ayutthaya . There , they finally faced a serious Siamese defensive line guarding the route to the capital , and Maha Nawrahta set up a garrison . The first major battle of the southern theatre ensued when the Siamese made a joint land - naval attack on the Burmese garrison . The naval force consisted of several war boats and a British ship which was used to bombard Burmese positions . But the Burmese defences held , and the Siamese retreated . The British ship fled to the sea . The Burmese army then marched north and was met by a Siamese force of 60 , 000 near west of the city . Outnumbered 3 to 1 , the more experienced Burmese army nonetheless routed the much larger Siamese army , which according to the Burmese , was " chopped to pieces " , forcing the remaining Siamese troops to retreat to the capital . Maha Nawrahta had now arrived at Ayutthaya as planned , in record time . " ( It took Alaungpaya ' s 40 , 000 men about three and a half months to arrive at Ayutthaya in 1760 whereas it took Maha Nawrahta ' s 20 , 000 plus army just about two months . ) " But he pulled back to the northwest of the city because he did not see Thihapate ' s northern army , and because he did not want to take on another major battle with his depleted army . He fixed his headquarters near the Pagoda built by Bayinnaung two centuries ago . He used the hiatus to refill the ranks with Siamese conscripts . Northern operations ( November 1765 – January 1766 ) . Meanwhile , Ne Myo Thihapate ' s northern army was still stuck in northern Siam although the pace of his advance had improved considerably since the end of the rainy season . After taking Kamphaeng Phet , Thihapate turned northeast , and captured the main northern cities of Sukhothai and Phitsanulok . At Phitsanulok , he paused to refill the ranks because in about 4 months , he had already lost many men to the grueling campaign and to " preventable diseases " . The local chiefs were made to drink the water of allegiance and provide conscripts to the Burmese army . ( Outside Ayutthaya , Maha Nawrahta too was collecting local levies . ) While the Burmese refilled their ranks , the Siamese command belatedly sent another army to retake Phitsanulok . But the Siamese army was driven back with heavy losses . It was the last major stand by the Siamese in the north . The Siamese defence collapsed afterwards . The Burmese army then moved down by boat the Nan River , taking Phichai , Phichit , Nakhon Sawan , and down the Chao Phraya , taking Ang Thong . They reached the environs of Ayutthaya on 20 January 1766 , making contact with Maha Nawrahta ' s army . Battle of Bang Rachan . According to Thai tradition , Ne Myo Thihapate ' s northern army was held up for five months at Bang Rachan , a small village northwest of Ayutthaya by a group of simple villagers . But the Burmese chronicles say that they only faced token opposition between Phitsanulok and Ayutthaya . First Chinese invasion of Burma ( December 1765 – April 1766 ) . In the mean time , an ominous situation had developed in the north for the Burmese . In response to Ne Myo Thihapate ' s recruitment campaign in the northern Shan states , which the Chinese considered their territory , the Qianlong Emperor ordered an invasion of Sipsongpanna and Kengtung . In December 1765 , as the Burmese waged the battles of Phitsanulok and Ayutthaya , a Chinese invasion force of 6000 invaded , laying siege to the Burmese garrison at Kengtung . Though battle hardened Burmese forces eventually drove back the besiegers , Burma was now fighting on two fronts , one of which had the largest army in the world . Nonetheless , Hsinbyushin apparently ( as it turned out , mistakenly ) believed that the border conflict could be contained as a low - grade war . He refused to recall his armies in Siam though he did reinforce Burmese garrisons along the Chinese border — in Kengtung , Kenghung and Kaungton . Battle of Ayutthaya . Battle at the outskirts ( January 1766 ) . While the Burmese garrison was battling the Chinese at Kengtung , the combined Burmese armies outside Ayutthaya were as strong as ever . Swelled by the Siamese levies , the combined Burmese invasion force now had 50 , 000 men , surpassing their pre - invasion strength . The Siamese army , which also gathered up 50 , 000 men , attempted a last - ditch effort to prevent a siege of the city . In late January , the Siamese forces came out and attacked Burmese positions centered around the Bayinnaung pagoda . Maha Nawrahta ' s army was on the west side of the pagoda and Thihapate ' s was on the east . The initial Siamese attacks focused on the west wing , gradually driving back Maha Nawrahta ' s army . But Thihapate ' s army outflanked the Siamese lines from the east , and succeeded in cutting the Siamese army in two . The Siamese vanguard which was pushing Maha Nawrahta ' s line was completely encircled . The ensuing battle wiped out much of the several thousand strong vanguard , and the rest were taken prisoner . The remaining Siamese troops retreated into the city and shut the gates . Early siege ( February – May 1766 ) . The Siamese command had made careful preparations to defend the capital . The fortifications consisted of a high brick wall with a broad wet ditch . The walls were mounted with numerous guns and cannon that they had stockpiled since the last Burmese war . Finally , they had banked on the advent of the rainy season , which had more than once saved the city in the past . They believed that if they could only hold out until the onset of the monsoon rains and the flooding of the great Central Plain , the Burmese would be forced to retreat . Realising that they had less than four months before the rainy season , the Burmese command initially launched a few assaults on the city walls . But the place proved too strong and too well defended . Because of the numerous stockades outside the city , the Burmese could not even get near the wall , and those that got near were cut down by musket fire from atop . The Burmese now drew a line of entrenchments round the city , and prepared to reduce it by famine . As time passed and no signs of surrender appeared , the approach of the dreaded rainy season caused alarm among the Burmese command . Several senior commanders advised calling off the invasion . However , Maha Nawrahta decided to continue the invasion , and his colleague Thihapate supported him . The Burmese command now made preparations to meet the rise of the river by collecting boats and building embankments on the bits of high ground . Rainy season ( June – October 1766 ) . When the rains came , the Burmese line of entrenchment round the city was swallowed up by the rising river . The Burmese were now broken up into several corps clinging on to artificial islands around the city . Seeing that the enemy was scattered into isolated camps , the Siamese attacked them in boats . The Burmese also had plenty of boats and met the Siamese boats in kind . In one of the naval battles , a Siamese commander while waving his sword and hurling defiance in the bows of his boat , was brought down by a musket shot , and the whole flotilla fled . In another encounter , one Siamese cannon shot scored a direct hit , killing several men on two Burmese boats . At any rate , the Siamese attempts to break the siege were unsuccessful . During this time , the Burmese troops farther back grew their own rice while their boats prevented supplies from entering the city . By the end of the monsoon season , the city was beginning to run low on provisions . Second dry season offensive ( November 1766 – March 1767 ) . When the waters subsided , the Burmese reconstructed the earthworks around the city , and gained more complete command than before . Some of the earthworks were higher than the walls , with cannon firing down on the city and the palace itself . Towards the end of 1766 , the governors of Tak and Phetburi led a waterborne expedition to relieve the city but were driven back . The governor of Phetburi was killed . The governor of Tak , Taksin , an able and ambitious commander , was blamed for the failed expedition , and hindered in his attempts to mount an effective counterattack . By then , the city was starving . To make matters worse , a fire broke out within the city in early 1767 that burned 10 , 000 houses . All was not well for the invaders either . In December 1766 , the Chinese launched their second invasion of Burma , directly aimed at Ava . Hsinbyushin , who had expected another Chinese invasion like the first one and had made preparations accordingly , was surprised by the sudden increase in the Chinese invasion force ( 25 , 000 versus 6000 in the first invasion ) . Still , the fiery king was unwilling to recall the armies from Siam ; instead he directed his remaining troops in northern Shan states to the Chinese front . He did however send a directive ( dated 9 January 1767 ) to his commanders in Siam to take the city quickly , and return as they were needed to defend the homeland . Indeed , when it appeared that the Chinese situation was contained , he later sent another directive to the Siamese front to " persevere " in the siege . Meanwhile , the Siamese leadership had grown desperate . The king and princes tried to escape the city but were driven back . The king finally offered to become a Burmese tributary but the Burmese , who had just received the king ' s order to persevere , would not accept anything less than an unconditional surrender . Shortly after , Maha Nawrahta died of illness , and by royal decree was buried with extraordinary honours . Ne Myo Thihapate now assumed the role of sole commander - in - chief . Sack of the city . By late March , the Burmese had dug tunnels to the walls , and mined them . At 4 pm on 7 April , several sections of the wall were brought down by the mines underneath , and the Burmese troops supported by artillery fire stormed the walls . ( Harvey reports the date as 28 March but the " Konbaung Hset " Chronicle gives Tuesday , 5th waxing of Tabaung 1125 ME , which is 7 April . ) The attackers finally breached the walls by sunset , and entered the city . The Siamese fought on inside the city but were eventually overwhelmed . Indiscriminate slaughter followed . Everything in sight was put to the torch . Even images of the Buddha were hacked for the gold with which they were coated . Tens of thousands of captives were led away to Burma in captivity . Virtually nothing was left of the 14th century Grand Palace , home to 33 kings of five dynasties , or the glittering Sanphet Prasat , used to welcome foreign envoys and state visitors . The Siamese king was found dead , identified by his brother Uthumphon . The Burmese brought Uthumphon and hundreds of Siamese nobles and members of the royal family to be resettled in Burma . The city of Ayutthaya , far greater than any in Burma , with a population said to rival contemporary London or Paris , was reduced to ashes by the " seemingly unstoppable Burmese military machine . " So it was that the Ayutthaya Kingdom founded in 1350 came to its final end . But Siam was soon to reemerge . Epilogue . Third Chinese invasion and Burmese withdrawal . For Hsinbyushin , his obsession to defeat Siam had come true . He now controlled a fragile empire that stretched from Manipur to Laos and Siam , which approximated Bayinnaung ' s 16th century empire . However he now faced a far more difficult task of holding it together , all the while waging a war against China . He had planned to leave behind a substantial garrison at Ayutthaya , either placing a protected Siamese prince on the throne or appointing senior Burmese officials to rule the country directly . But because he had to allow Shan , Laotian and Siamese levies , some of whom had been away from home for nearly two years , to return home , Hsinbyushin had a limited number of forces available to him in the second half of 1767 . Still , the recalcitrant Burmese king tried to hold on to all his gains . To reinforce the Chinese front , he recalled from Siam a major portion of the army , which arrived back to Ava with the Siamese captives in July 1767 . As it turned out , the remaining Burmese forces in Siam , which could not have been more than 10 , 000 at most , were too scattered among many garrisons , and too small to hold the conquered kingdom together . Indeed , the Burmese had little control outside their garrisons , and no control over the Siamese countryside where gangs of bandits roamed . As it soon proved , Hsinbyushin ' s two - front policy was utterly unsustainable , and would nearly cost Burma ' s independence . With the majority of Shan levies not available , the entire Burmese defences only had about 20 , 000 men at the start of the third Chinese invasion in November 1767 . Hsinbyushin apparently thought the size of his defences was adequate for a similar size Chinese force of the second invasion . But the next Chinese invasion proved to be the largest yet — 50 , 000 strong , and caught the Burmese command by surprise . The Chinese , led by their elite Manchu Bannermen , quickly overran outnumbered Burmese defences and barreled down towards Ava , and by December Hsinbyushin was finally forced to recall all his remaining troops from Siam . He sent them directly to the front in Shan states where the Burmese were conducting a guerrilla warfare against Chinese supply lines . " ( The main Chinese force ultimately reached just north of Ava by February 1768 . Hsinbyushin was down to the last 12 , 000 men to defend his capital . ) " Bolstered by the returning troops from Siam , the Burmese defences recovered . The Chinese forces were driven back with heavy losses in March 1768 . After the close - call , Hsinbyushin kept almost all his troops on the Chinese front . Better prepared , the Burmese forces defeated the next Chinese invasion at the end of 1769 at the border . Commanders from both sides signed an uneasy truce , which was not accepted by both governments . The Chinese kept a heavy military lineup in the border areas of Yunnan for about one decade in an attempt to wage another war while imposing a ban on inter - border trade for two decades . In the following years , Hsinbyushin was forced to keep his defences along the Chinese border and could not renew his Siamese adventures . In the mean time , much of the Burmese gains of 1765 – 1767 in Siam had gone to waste . An energetic leader had emerged to reunify Siam , and make her a formidable power in the following decades . Siamese civil - war and emergence of Taksin ( 1767 – 1770 ) . After the fall of Ayutthaya , the Burmese had little control over the Siamese countryside . After the Burmese left , five Siamese polities — Phitsanulok , Sawankhalok , Nakhon Si Thammarat , Phimai , and Chanthaburi — vied to fill the power vacuum . Of the five , Taksin , based out of Chanthaburi since June 1767 , was to reunify Siam in the next three years . He emerged the main contender by late 1768 . Taksin ' s first attempt at reunification — an expedition to Phitsanulok in May 1768 — was unsuccessful . He captured Phimai at the end of 1768 , and was crowned monarch in December 1768 . By late 1769 , he had defeated Nakhon Si Thammarat . In mid - 1770 , he finally defeated Phitsanulok , and became the sole ruler of Siam . Territorial changes . For all the fighting and destruction , the Burmese gained only the lower Tenasserim coast . It is likely that even the retention of Tenasserim was possible only because the Siamese were immersed in their civil war . A more united Siam would have likely retaken at least the lower Tenasserim coast , if not the upper coast since almost all Burmese troops were deployed on the Chinese front throughout 1768 and 1769 . ( Recall that Ekkathat , widely considered to be an ineffective ruler , was able to retake the lower coast in 1761 while Naungdawgyi had his hands full with multiple rebellions . A much more able leader like Taksin would certainly have retaken Tenasserim if it were not for the civil war . ) But the Sino - Burmese war ended in December 1769 about six months before Taksin finished reunifying mainland Siam . Taksin chose not yet to renew the war with the Burmese , instead chose to focus on consolidating his gains in mainland Siam . ( The Siamese would not launch an offensive war against the Burmese until 1787 . ) The territory of Tenasserim , with over 800 islands , which had been under Siamese rule for nearly five centuries , passed to the Burmese . Geopolitical situation to the next war ( 1768 – 1776 ) . Aside from acquiring the lower Tenasserim coast , the Burmese did not achieve their larger objectives of taming Siam and securing their peripheral regions . The actual outcome was the opposite . The new energetic Siamese leadership was now better able to support rebellions in Lan Na and Lower Burma . On the other hand , the Burmese offensive military capability was greatly diminished after two long wars with Siam and China . In the following years , Hsinbyushin was totally preoccupied with yet another Chinese invasion . At any rate , the Burmese could not blame the Siamese for fomenting the rebellions of the 1770s . It was mainly the warlord behaviour of Burmese commanders who " were drunk with victory " that incited the rebellions . The Siamese were only helping the ready situation on the ground . In 1773 , the southern Burmese army command provoked a mutiny by its ethnic Mon troops and put down the mutiny with " undue severity " . Over 3 , 000 Mon troops and their families fled to Siam , and joined the Siamese army . The army command warlord ' s behaviour only grew in 1774 when Hsinbyushin suffered from a debilitating long illness that would ultimately claim his life two years later . Local governors began to disregard the king ' s royal orders , an unimaginable development only a few years previously . In January 1775 , another Lan Na rebellion started with full Siamese support . Chiang Mai fell on 15 January 1775 . Hsinbyushin on his deathbed ordered his last invasion of Siam in 1775 . The Siamese defences held this time . The Burmese armies were bogged down in central Siam in June 1776 when they withdrew after the news of Hsinbyushin ' s death had reached the front . Lan Na was firmly on the Siamese camp . The over two century Burmese rule of Lan Na had come to an end . Analysis . The war came at the near peak of Konbaung military power . ( Their victory over the Chinese is considered the peak . ) According to Lieberman , the " " near simultaneous victories over Siam ( 1767 ) and China ( 1765 – 1769 ) testified to a truly astonishing elan unmatched since Bayinnaung . " " To be sure , it was not so much that the Burmese had more troops or superior weapons ; they did not . The main reason for Burmese victory was the same as that in the 1760 war : the Burmese , who had been in successive wars since 1740 , simply had experienced , proven , confident commanders , while most Siamese command had little battlefield experience except in the 1760 war . Specifically , it was the Burmese commanders ' ability to lead a multi - ethnic army which consisted of regiments from various parts of the empire that made the invasion even possible . ( Upper Burma , the home of Konbaung Dynasty , alone could not have launched an offensive war against a more populous Siam , without its policy of having the conquered lands contribute to its next war effort . ) In this war , the Burmese command was able to inspire ( or push ) their troops . Historian Harvey writes : " " When roused , the men fought with spirit , vying among themselves as to who should first mount the wall ; " although he wonders why : " " They died like flies from preventable disease , and suffered ghastly wounds for which they received no thanks from the King , as the loss of a limb , even in honourable service , disqualified a man from entering the palace : His Majesty ' s sight must not be sullied by reality . " " Equally important , the Burmese commanders were able to motivate their Siamese levies , which by the battle of Ayutthaya made up a significant minority of the Burmese army . The Siamese participation in the Burmese army highlights the fact that the war was between the rulers , not between nations . On the other hand , despite having made extensive preparations , when the actual war came , the Siamese command proved belated and uncoordinated . In all , they appeared to have relied much on the defences of Ayutthaya , perhaps thinking that the Burmese would not be able to lay siege beyond the dry season . According to the Burmese chronicles , the southern Burmese army faced an easier time than in 1760 . ( They faced token opposition until it reached Nonthaburi , dangerously close to Ayutthaya . In contrast , the Siamese put up several spirited defensive stands in 1760 , greatly slowing down the Burmese advance . ) The Burmese would not make any progress against a better - led Siam in the future . This was the last war in which the Burmese were able to get near Ayutthaya , and achieve territorial gains . The Burmese performance got progressively worse over the next decades , and lost territory . They managed to penetrate to central Siam in 1775 – 1776 but were decisively defeated at the border in 1785 – 1786 , after which the Burmese would no longer attempt another full scale invasion . Significance . Resurgent Siam . Perhaps the most important legacy of the war was the reemergence of Siam as a major military power in mainland Southeast Asia . The war replaced the " ancien régime " of Ayutthaya and brought in a new energetic dynasty . In the following years , the new Siamese leadership would go on to challenge the Burmese in Tenasserim , Laotian states , Lan Na and Kengtung , and redress Siam ' s " historical military inferiority to Burma " . A resurgent Siam assembled an empire , swallowing western Cambodia as well as Burmese vassals / tributaries of southern Lan Na ( 1776 ) , Vientiene ( 1778 ) , Chiang Saen ( 1786 ) , and Luang Phrabang ( 1792 – 1794 ) . The confident Siamese even attempted to acquire Kengtung and Sipsongpanna , lands so far away from their Bangkok base , from the Burmese in 1803 – 1804 . By the early 19th century , Siam was one of three main powers in mainland Southeast Asia , along with Burma and Vietnam , and had the second largest empire in all of Southeast Asia after the Burmese empire . After the First Anglo - Burmese War of ( 1824 – 1826 ) removed the Burmese threat to Siam , the Siamese empire expanded eastwards unchecked , annexing all Laotian states and western Cambodia until they ran into Vietnamese forces in the middle of Cambodia in 1840 . Siamese influence on Burmese culture . The Siamese captives carried off from Ayutthaya went on to have an outsize influence on traditional Burmese theatre and dance . In 1789 , a Burmese royal commission consisting of Princes and Ministers was charged with translating Siamese and Javanese dramas from Thai to Burmese . With the help of Siamese artists captured from Ayutthaya in 1767 , the commission adapted two important epics from Thai to Burmese : the Siamese Ramayana and the Enao , the Siamese version of Javanese Panji tales into Burmese Yama Zattaw and Enaung Zattaw . One classical Siamese dance , called Yodaya Aka ( lit . Ayutthaya - style dance ) is considered one of the most delicate of all traditional Burmese dance s . Impact on Thai - Burmese relations . The legacy of the war has lingered on negatively on the Burmese – Thai relations ever since . Thai perspectives . The fall of Ayutthaya is considered one of Thailand ' s greatest national calamities . A Siamese chronicler wrote : " The king of Hanthawaddy ( Bayinnaung ) waged war like a monarch but the king of Ava ( Hsinbyushin ) like a robber . " In 1917 , Siamese prince Damrong Rajanubhab published a highly nationalist history of the centuries long hostility between the two countries , " Our Wars with the Burmese ( Thai Rop Pharma ) " , which had a major influence on the development of Thailand ' s view of its national history , as found in school text books and popular culture . In his view , not only were the Burmese a savage and aggressive people but Siam was defeated in war only when it was unprepared and divided against itself . Kings who rallied the people , such as Naresuan and Rama I , waged successful wars of national liberation against an imperialist enemy . Thus ancient battles between rival rulers suddenly became wars between nations . More recent scholarship has cautioned against casting the history of the 16th and 18th centuries in a 20th - century conceptual framework . Historian Donald Seekins writes that " the 24 Thai – Burmese wars described by Damrong were wars between Monarchs rather than between nations " , and that " many prominent Siamese of the era , including Naresuan ' s father , were willing to accept Burmese overlordship " . Another historian Helen James writes that " these wars were primarily struggles for regional and dynastic supremacy and were neither national nor ethnic conflicts . " After all , many Siamese levies participated in the attack on Ayutthaya . This view is echoed by modern Thai academics such as Nidhi Eoseewong and Sunait Chutintaranond . According to Sunait " The negative attitude toward the Burmese does not occur solely as a result of the past relationship . It is , rather , the outcome of political manoeuvers by the Thai nationalist governments , especially military regimes . " Nonetheless , the modern academic viewpoints have not replaced Damrong ' s viewpoints in Thai schoolbooks , or popular culture . This has fostered a feeling of enmity among the Thai people towards the Burmese , and has coloured the Thai - Burmese relations to the present day with real political ramifications . This enmity at least in the Thai political leadership manifested in the Thai " buffer zone " policy , which has provided shelter , at various times and has actively encouraged and " sponsored " , the several ethnic resistance groups along the border . Burmese views . In December 1954 , U Nu , the first prime minister of the Union of Burma , on his first state visit to Bangkok , publicly apologized for Burma ' s past misdeeds . However , most Burmese today only know superficially about their past kings ' invasions . Most know little about the destruction and atrocities committed by the Burmese troops in Siam because Burmese school books simply do not mention them . Many Burmese fail to realize some of the historical reasons behind the Thai enmity , and the Thai governments ' buffer zone policy . Many Burmese , especially those in the military , remain sceptical of the Thai governments ' assurances that it would not tolerate any activities that " undermine stability of neighboring countries " .