Born c. early 1393,[note 1] Binnya Dhammaraza was a son of King Razadarit of Hanthawaddy (r. 1384–1421).
[note 2] According to the Pak Lat Chronicles, his childhood princely title was Binnya Kyan (Mon: ဗညာကေန်, Burmese: ဗညားကျန်း, [bəɲá tɕáɴ]).
As the eldest living son of Razadarit,[note 3] the prince grew up as the heir-presumptive at the royal palace in Pegu (Bago).
[5][7] The performance won him the honor of defending the capital Pegu in 1414–1415 when Razadarit decided to retreat to Martaban.
On 13 March 1415, in one of the most famous battles in Burmese military history, Dhammaraza's vanguard regiment took on Minye Kyawswa.
Although he was driven back and other Hanthawaddy forces were nearly defeated, the crown prince of Ava was mortally wounded in the battle.
In 1416, Razadarit appointed Dhammaraza to lead an invasion of Toungoo (Taungoo), Ava's southeastern territory.
[14] In any case, when Razadarit suddenly died from a hunting accident in 1421, the still energetic 53-year-old king had not formally anointed an heir-apparent.
He had at most given only governorships to his sons: Dhammaraza at Martaban (Mottama), Ran at Syriam (Thanlyin), and Kyan at Dala (Twante).
Dhammaraza's chief rival was Ran, who was only a few months younger than him, and deemed the alternative by the court.
Although Chief Minister Dein Mani-Yut did not take sides between Dhammaraza and Ran,[15] the eldest prince apparently garnered enough support at the court to be crowned king at Pegu.
[18] Upon Dhammaraza's accession at Pegu, Ran and Kyan immediately revolted out of fortified towns just within 120 km south of the capital.
Thihathu, who himself had ascended the Ava throne just two months before Dhammaraza's accession at Pegu, quickly sent down two regiments (2000 troops).
[17] Knowing that Ava would return in the dry season, Dhammaraza desperately tried to keep the support of his brothers by sharing power.
[21] As soon as Kyan left for Martaban, Ran brazenly occupied Dala and Dagon, which belonged to the Pegu province.
[note 5] It was Ran's delta region that 14,000-strong Ava forces led by Gen. Thado and Prince Min Nyo invaded by land and river.
A month into the siege, in January 1423, Ran proposed a marriage alliance by offering his younger sister Shin Saw Pu to Thihathu.