He looked for and secrelty killed the strongest and bravest of Ayutthaya's defenders. In 1569 A.d>, under the command of King Bayinnuang, the Burmese armies captured Ayutthaya and gained control of the kingdom. Tens of thousands of Ayutthaya citizens and the royal family were taken to Burma, amongst whom was Phra Naresuan.
Phra Mahathamraja, the father of Phra Naresuan was appointed ruler of Ayutthaya under the supervision of the Burmese.
After being held as a hostage in Burma for fifteen years Phra Naresuan was able to return to Ayutthaya and declare its independence. He had heard of the King Nandabayin )King Bayinnuang's son) assassination plan. Phra Naresuan strengthened the city's defences and increased Ayutthaya's influence in the Northern regions. In 1590 A.D., King Theamarafa died, and Prince Naresuan became King at the age of 35. In the year 1592 A.D., at Nong sarai, King Naresuan fought a great battle with the Burmese, in which the Burmese Crown Prince (King Nandabyin's son) was killed. The Burmese army fled and the Burmese were driven out of Siam.