Invasion of Pegu[edit]
King Naresuan entered Hanthawadi (now Pegu), mural painting by Phraya Anusatchitrakon, Wat Suwandararam, Ayutthaya.
Main article: Siege of Pegu (1595)
Naresuan eventually marched his troops to Pegu in 1595.He laid siege on the city for three months but was unable to enter. The huge forces of the Lords of Pyay, Toungoo, and Ava then arrived to free Pegu. Naresuan decided to retreat.
Main article: Burmese–Siamese War (1594–1605)
The Lord of Pyay staged a rebellion against Nanda Bayin in 1595, followed by Toungoo, Rakhine, Lanna, and Lan Xang. King Nokeo of Lan Xang prepared to march through Lanna to Pegu to rescue the Laotian captives. Noratra Mangsosri of Lanna (Nanda Bayin's brother) then put his kingdom under Siamese tributary to get Ayutthayan supports. Naresuan sent Siamese forces to prevent Laotian forces from entering Lanna.
After the series of upheavals in the Burmese Empire, Naresuan decided to invade Pegu again in 1599. Naresuan allied himself with Rakhine. However, the Lord of Toungoo feared that if Naresuan had taken Pegu the Siamese power would have been too large and might engulf Toungoo itself. So, the Lord of Toungoo has plan to help Pegu from Siam invasion.