Ayutthaya employed traditional defense strategies by relying on the supposed impregnability of its walls and the incoming of the rainy flooding season.

The Burmese, however, circumvented these strategies by persisting to stay in rainy season and by the tactics of destroying Ayutthaya city wall at the roots.

In the northern front, Ekkathat sent Chaophraya Phrakhlang the Siamese Prime Minister to lead an army of 10,000 men to halt Nemyo Thihapate.

This left the periphery even less defended as western and northern Siamese towns fell prey to Burmese conquests in rapid succession.

With the Burmese victories at Paknam Prasop and Wat Phukhaothong in January 1766, they were able to set foot on the Ayutthayan outskirts to lay siege to the Siamese royal city by February.

The gates were decorated with flared crosspieces at the top similar to the Giant Swing in modern Bangkok and were designed to impress rather than to keep enemies out.

The Siamese government purchased a large number of Western-produced, cast-iron, larger-caliber cannons known in Thai as "Bariam" (from Malay Meriam).

Food supply was plentiful inside the city, as a French missionary observed that "the provisions of the capital were not yet exhausted, the beggars alone suffered from hunger and some died of it".

After his defeat, Phraya Tak chose not to return to the Ayutthaya citadel and instead stationed his troops at the Wat Phichaisongkhram temple on the eastern wall across the city moat.

In November 1766, ten days after the Siamese defeat at Wat Sangkhawat, King Ekkathat sent another force to attack Nemyo Thihapate to the north.

[10] By November 1766, after the two devastating defeats at Wat Sangkhawat and Phosamton, according to Burmese chronicles, both the Siamese court and populace trembled in fear and anxiety[8][10] as they realized their situation had become dire.

[21] Phraya Tak was a Siamese nobleman of Teochew Chinese immigrant background with the personal name Zheng Xin (鄭新).

On 4 January 1767, Phraya Tak and his followers broke through the relatively less-manned Burmese encirclement to the east to seek out a new position in Eastern Siam.

[26] Liu Zao (劉藻), the viceroy of Yungui, committed the Qing Green Banner Army to attack Kengtung in 1765, which was repelled by the Burmese commander Nemyo Sithu.

Yang Yingju sent Chinese armies through the Tiebi Pass (鐵壁) in October 1766 to directly attack the Burmese heartlands in the Irrawaddy valley.

The Portuguese community at Ban Portuket, about 1.5 kilometer downstream to the south of Ayutthaya, had been left isolated since November 1766 when the Burmese closed in.

"[27] By February 1767, the Chinese stockade at Khlong Suan Phlu and the Portuguese camps at Ban Portuket were the main Siamese defense line to the south.

In February 1767, the Siamese took out an old cannon named Dvaravati,[18] which was believed to be spiritual guardian of the Ayutthaya city, to be employed at the front to fire at Nemyo Thihapate's position to the north.

According to Prince Damrong, the death of Maha Nawrahta was detrimental to the Siamese as it allowed the Burmese forces to be united under the single command of Nemyo Thihapate.

The Burmese held Catholic priests as hostages, demanding the surrender of Pierre Brigot, the apostolic vicar at Saint Joseph seminary, promising not to destroy Christian churches.

[10] The Battle of Huaraw was intense as Siamese soldiers stepped on the dead bodies of their comrades to climb their portable ladders into the forts.

Thai chronicles described supernatural events before the eventual Fall of Ayutthaya in April 1767 including Buddha statues crying and splitting.

[21] The Burmese put wood logs into the tunnel to set fire to the base of the northeastern section of the Ayutthayan wall at Huaraw.

The remaining Siamese forces of 10,000 men inside of the citadel, under the command of Chaophraya Phrakhlang and Phraya Kalahom, continued to resist in their last stand.

The Burmese conquerors indiscriminately slaughtered Ayutthaya citizens, plundered for wealth and burnt down all buildings including palaces and temples.

[7] Siamese wealth including precious gems and metals, elephants, horses, Buddhist scriptures and academic treatises were also taken by the conquerors.

[10] The Phra Si Sanphet Buddha image, which stood about sixteen meters tall, was cast in 1500 AD and had been the palladium of the Ayutthaya kingdom for centuries, was destroyed and molten down by the Burmese.

With the city completely destroyed, it was therefore unsuitable for the victorious Burmese to set up a large garrison there owing to the total lack of shelter resultant of its destruction.

The Burmese thus only left a small garrison in the city, with the rest of their forces either holding onto conquered territory or, in the case of their Shan and Lao contingents, were even demobilized out of confidence over their recent success and victory.

[34] But while Ayutthaya eventually came back into Siamese possession seven months after it fell to the enemy, it never again regained its grandeur nor recovered as a major city.