Burma reconstituted into a militarized polity, whereas Siam, centered on Ayutthaya, had not faced any serious external threats or military conflicts since late seventeenth century and Siamese defense system had been largely in disuse.

[10] Alaungpaya and his Burmese forces of 40,000 men left Rangoon to invade Siam in late December 1759,[9] with his second son Prince Thiri Damayaza of Myedu (later King Hsinbyushin) and his childhood friend Minkhaung Nawrahta as vanguard commanders.

Gharib Niwaz led his Manipuri armies to invade and plunder Northwestern Burmese towns along the Chindwin and Mu rivers including Myedu, Tabayin and Mingin.

In 1744, in response to Siamese support to Burma, Smim Htaw sought alliance with Lanna by marrying a daughter of King Ong Kham of Chiang Mai as his second queen.

Finally in 1751, Binnya Dala sent the Mon forces of 27,000 men under the command of his younger brother Upayaza with his another sibling Talaban as vanguard along the Irrawaddy north to attack the Burmese royal seat of Ava.

On his deathbed in 1733, King Thaisa gave the throne to his two sons instead of his younger brother Prince Phon, who had been the Wangna and technically heir presumptive, resulting in a civil war in Ayutthaya between the uncle and his nephews.

In February 1752, about one month before the eventual fall of Ava, Aung Zeiya declared himself Alaungpaya or Future Buddha Bodhisattava, becoming a Minlaung[31] or royal claimant and founding the Konbaung dynasty.

Throughout history, both Burma and Siam had claimed the entire Tenasserim coast (present-day Mon State and Tanintharyi Region in Myanmar) and control had changed hands several times.

[38] In 1683, King Narai of Siam, at suggestion of his First Minister Constantine Phaulkon, appointed a former British East India Company employee Richard Burnaby to be the governor of Mergui.

Burnaby and his harbormaster Samuel White went out of Siamese control in their attempts to establish their own personal dominance over the trades of the Bay of Bengal by building a large fleet and attacking rival merchant ships in 1685.

After his return to Shwebo from Manipur campaign in February 1759, Alaungpaya took off on his pilgrimage trip, along with his queen, his sons and his family, to Rangoon for dedication of Zayat or pavilion to the sacred Shwedagon Pagoda and for other merit-making activities.

Harvey) outright downplay the aforementioned reasons as "pretexts", and have suggested that the primary cause of the war was Alaungpaya's desire to restore Bayinnaung's empire (which included Siam).

Hall writes that the "chronic raiding" by the Siamese and Mon rebels "alone would have provided an adequate casus belli" although he adds "for a monarch unable to settle down to a peaceable existence".

The Burmese then began to assemble their invasion force, starting during their new year celebrations in April 1759, gathering troops from all over Upper Burma, including from recently conquered northern Shan States and Manipur.

[9] In December 1759, Alaungpaya dispatched a royal letter to Thomas Arthur, comte de Lally the governor of Pondicherry, urging the French to resume trade relations with Burma.

Khun Rong Palat Chu led his army of 500 Phrai commoner men to wait for the Burmese at the Wakhao[12] beach in modern Tambon ฺBonok, Mueang Prachuap Khiri Khan district.

Opposition to Alaungmintaya who is destined to become supreme is hopeless.Alaungpaya's royal message was written in Thai and Burmese languages and placed in casket to be delivered by a young Siamese monk from Phetchaburi to King Ekkathat at Ayutthaya himself.

During these defensive preparations, Uthumphon flexed his political power by arresting Ekkathat's supporters including the unpopular brothers Phraya Ratchamontri Pin and Chamuen Si Sorrarak Chim.

In late March 1760, in response to the Burmese invasion, Ayutthaya experienced leadership turnover and political rearrangement, in which pro-Ekkathat supporters were purged and pro-Uthumphon officials were restored to power.

Alaungpaya sent his vanguard forces under Minkhaung Nawrahta to take position at Phosamton, a suburb to the north of Ayutthaya, which had been granted as a community for the Mon refugees[30] by King Borommakot back in 1747.

Prince Thiri Damayaza of Myedu, Alaungpaya's son, told his father that Siam's blank promise to send tributes was only to buy time for the rainy season to arrive.

Alaungpaya had left his royal city of Shwebo in July 1759[8] but spent the majority of his time dealing with the British at Negrais and making merits at the Shwedagon Pagoda at Rangoon.

After entering the Gulf of Siam Coast, Burmese commanders, finding Siamese military defense incredibly weak, rushed in competition to seek glory for the inevitable conquests.

In the late sixteenth century, King Naresuan had utilized more active defense strategy by reaching out to deal with the invaders at the frontiers and periphery instead of passively standing in the Ayutthayan citadel.

In Thai historiography, the only valiant figure in this war was Khun Rong Palat Chu, a mid-ranking officer who made a desperate stand against the overwhelming Burmese forces at Wakhao beach[12] in modern Prachuap Khiri Khan.

Eventually, Siamese traditional strategy of passive defense succeeded for the last time as King Alaungpaya and the Burmese were obliged to retreat in April 1760 by the upcoming arrival of rainy season.

Naungdawgyi considered Chiang Mai providing shelter to Talaban and also viewed Lanna or modern Northern Thailand as a part of traditional Burmese area of influence.

The new king Hsinbyushin appointed Abaya Kamani as the Myowun or governor of Chiang Mai and promoted Minhla Thiri to title Maha Nawrahta for their meritorious services.

Nemyo Thihapate initiate his attack on Siam by marching his Burmese-Lanna forces in August 1765[62] down south, much earlier than his colleague Maha Nawrahta at Tavoy due to the northern path to Ayutthaya being much longer.

Failing to dislodge the besieging Burmese, by February 1766, Ayutthaya resorted to traditional strategy of passive stand against the invaders, waiting for the rainy season to come and relying on the formidable Ayutthayan wall to protect the city.