The war reached stalemate until Maha Thiha Thura decided to disrupt the Siamese supply line, leading to the Fall of Phitsanulok in March 1776.

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.

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.

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.

[11] 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.

[13] The emperor blamed Han Chinese Green Standard regiment for failures and began to employ Manchu bannermen in the Burmese campaign.

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.

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[13] (阿桂).

As Burma did not actually send those said missions to China, Emperor Qianlong ordered the shutdown of the Sino–Burmese borders,[13] disrupting the trade at the expense of local Chinese and Shan merchants.

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[1] as the new governor of Martaban to organize forces to invade Siam in 1772.

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.

The Mon forces continued marching and managed to temporarily take control of Yangon but were eventually repelled by the Burmese rescue armies.

[1] After about one and a half month of isolation with minimal food and water, Satpagyon Bo and the Burmese at Bangkaeo surrendered and submitted to King Taksin on March 31, 1775.

[17] The strategy of King Hsinbyushin to invade Siam from two directions and converge was foiled by the Siamese capture of Chiang Mai and the Mon Rebellion at Martaban.

[2] Phitsanulok had been the Mueang Ek or political administrative center of Northern Siam since the Ayutthaya Period with Chaophraya Surasi Boonma as the governor since 1770.

Chakri and Surasi at Chiang Mai, upon learning of the Burmese invasion at their back, marched their armies to return to Sukhothai with great haste.

[17] Maha Thiha Thura stayed at Kongthani for two months to gather resources while Chaophrayas Chakri and Surasi established the defenses at Phitsanulok.

Chaophrayas Chakri and Surasi personally led the Siamese forces to assault on Burmese lines to break the encirclement many times but did not succeed.

[2] King Taksin then had Satpagyon Bo, together with other Burmese captured generals and the remaining followers of Chao Phra Fang executed to ensure the security of Thonburi.

Maha Thiha Thira broke this stalemate by ordering his rearguard at Kongthani to march south to attack Siamese supply line at Nakhon Sawan.

Taksin told Surasi that he was planning to move the royal base to Nakhon Sawan to protect the supply line and to wait for Maha Thiha Thura to run out of his resources.

On March 15, 1776, Chaophrayas Chakri and Surasi managed to break free from the Burmese at Phisanulok and regrouped at Banmung and Chomphu to the east of Phitsanulok.

In haste, Maha Thiha Thura decided to leave his generals and forces in Siam and immediately left for Ava, taking Northern Siamese captives and valuables with him to Burma.

Chakri and Surasi then led the remaining Siamese defenders down south to Saraburi and marched north to pursue the retreating Burmese at Sukhothai.

[17] King Taksin and Phraya Yommaraj Mat (son of Chaophraya Chakri Mud) stationed at Phichit, where they received the Northern Siamese refugees from Phitsanulok.

[1][2] As Maha Thiha Thura returned to Burma, the remaining Burmese forces in Siam ran free to pillage Siamese countryside for about five months and the war resorted to guerilla warfare.

[21] If Hsinbyushin had not died during the war, it would be possible that Maha Thiha Thura would conduct full-scale offensives on the city of Thonburi and Siam might fall to the Burmese again.

[17] Nine years later in 1785, during the Nine Armies' War, these three Northern cities were so thinly-populated that they were unable to raise adequate manpower to fight the invading Burmese from the north and were evacuated.

Upon hearing the news of the death of Hsinbyushin, Maha Thiha Thura, despite being in the middle of warfare, rushed back to Ava to secure the succession of his son-in-law.