Toungoo dynasty Burmese sources: Bayinnaung's five armies Invasion force: 54,600 men, 5,300 horses, and 530 elephants [2] Combined with Phitsanulok army: 106,000 Siam Including Naresuan The Burmese–Siamese War (1568–1569) also known as the War of the first fall (สงครามคราวเสียกรุงครั้งที่หนึ่ง) was a military conflict fought between the Kingdom of Ayutthaya (Siam) and the Kingdom of Burma.

In the following years, Mingyi Nyo managed to retain the kingdom's independence while also leading several successful campaigns against Mon states.

42 days later Chinnarat was assassinated by nobles loyal to the Suphannaphum Dynasty, who installed Chairacha's relative as King Maha Chakkraphat.

The Burmese–Siamese War (1547–49) resulted in the Burmese capture of the Upper Tenasserim coast down to Tavoy, while Ayutthaya managed to protect the rest of its territory.

Maha Chakkraphat's refusal to grant the Burmese king Bayinnaung with two white elephants served as the casus belli of the conflict.

The Burmese first took Phitsanulok, Sawankhalok, Kamphaeng Phet, and Sukhothai thus turning them into tributary states, denying Ayutthaya valuable allies.

Siharat–Dejo instead remained in Phitsanulok and disclosed Maha Chakkraphat's true intentions, pushing Burma into an armed intervention.

[13] Having gained the support of northern Thai states, Bayinnaung amassed five armies that consisted of 54,600 men, 5,300 horses, and 530 elephants according to Burmese sources.

The Lan Xang forces prevailed at which point one of the commanding generals from Nakhon Phanom broke south toward Ayutthaya.

[14][4][16] The Burmese took several weeks to regroup and rest having taken Ayutthaya, which allowed Lan Xang to rally their forces and plan for prolonged guerrilla warfare.