He then leveraged the coastal kingdom's wealth, manpower and access to Portuguese mercenaries and firearms, and extended his rule to the ancient capital of Pagan (Bagan) in 1544.

He actively courted the support of ethnic Mons of Lower Burma, many of whom were appointed to the highest positions in his government and armed forces.

He grew up playing with children of his servants, including one Ye Htut, the eldest son of Mingyi Swe and his wet nurse Myo Myat.

[5] The young crown prince grew up having to live up to a prophecy at his birth, which claimed that he would grow up to be a great warrior just like Minye Kyawswa.

[7] According to prophecy, Tabinshwehti was the reincarnation of a prince named Minye Kyawswa who had been put to death by his father King Dhammazedi of Hanthawaddy.

[10] His first experience with warfare came in 1525 when Ava's forces led by King Narapati II unsuccessfully laid siege to Toungoo from April to May.

[note 3] In the following years, his father's little principality gained more manpower as refugees from Upper Burma in search of a safe haven streamed in.

[14] The young king's first important decision came c. April 1534,[note 4] when the affair between his half-sister Thakin Gyi and his right-hand man Ye Htut was discovered.

Tabinshwehti deliberated at length with his ministers, and finally came to the conclusion that Ye Htut should be given his sister in marriage, and a princely title of Kyawhtin Nawrahta.

In late 1532, the Confederation of Shan States, already ruling much of Upper Burma, attacked its erstwhile ally Prome, and sacked the city.

[19] In the next 16 years, Tabinshwehti along with his deputy Kyawhtin Nawrahta (later Bayinnaung) would go on to unite many of the petty kingdoms that had existed since the fall of the Pagan Empire in 1287.

Indeed, about two and half years earlier,[note 5] Tabinshwehti and his chosen men (eight ponnas, 40 ministers, and a company of 500 most-skillful horsemen led by Kyawhtin Nawrahta) had made an uninvited foray into the Shwemawdaw Pagoda at the outskirts of Pegu, the capital of Hanthawaddy, ostensibly for the king's ear-piercing ceremony.

However, the offer was promptly rejected by the wealthy port's ruler Saw Binnya, who had heavily fortified his city and enlisted several Portuguese naval and land mercenaries.

Finally, right before the rainy season in May 1541, Adm. Smim Payu's flotilla broke through the seven Portuguese warships guarding the harbor, and the city fell.

[26] The conquest of Martaban now gave his upstart regime complete control of Lower Burma's manpower, access to foreign firearms and maritime wealth to pay for them.

[30][note 6] In retaliation, the Confederation, now consisting of seven Shan states, led by King Hkonmaing launched a major land and naval invasion (16,000 army troops, 1000 horses, 120 elephants, 1200 naval troops, 30 large war boats, 30 fast war boats, and 50 cargo ships) on 7 December 1543.

[31] At the ancient capital, Tabinshwehti was crowned in the full ritual and ceremony of the great kings of Pagan,[32] and made a triumphant return to Pegu in July/August 1544.

[36] The next day, Toungoo forces began their final push, driving out the Mrauk-U army from Launggyet and surrounding the heavily fortified Arakanese capital.

[37] Meanwhile, Tabinshwehti received news that Siamese forces had occupied the Tavoy (Dawei) frontier up to Ye (modern southern Mon State).

Next year, near the end of the rainy season on 14 October 1548, 12,000 strong Toungoo forces led by Tabinshwehti and Bayinnaung invaded Siam via the Three Pagodas Pass.

The crew set up camp at Pantanaw where they spent weeks in search of a white elephant, considered extremely auspicious in Burmese tradition.

Tabinshwehti came to power at a time when the prevailing administrative model in mainland Southeast Asia was that of small solar polities, which consisted of a high king surrounded by semi-independent tributaries and autonomous viceroys.

His administratively fragile kingdom proved to be the impetus for the eventual reunification of the entire country under Bayinnaung, even if the core of the reunified Burmese state would stabilize only in the early 17th century.

[58] Though he may initially have been urged on by his court, it was ultimately his decision to start a war with a wealthier but poorly led neighbor, and to persist until the victory over Hanthawaddy was achieved.

He quickly built on the success by combining his kingdom's "more martial tradition" with the maritime wealth and manpower of Lower Burma, which enabled him to acquire foreign mercenaries and firearms.

His success in breaking out of an increasingly narrow dry zone not only saved the only remaining ethnic Burman-led kingdom from extinction but also ensured the continued spread of Burmese culture and language in the Irrawaddy valley.

Tabinshwehti went to great lengths to ensure that the rise of his regime did not come at the expense of Lower Burma's ethnic Mon culture and language.

According to the historian Victor Lieberman, had later Toungoo rulers continued Tabinshwehti's policy of "Mon–Burman synthesis", ethnic relations within the Irrawaddy valley "might have moved along a very different path".

"[60] Tabinshwehti is still remembered as a brave king and empire builder in popular culture, albeit generally in a secondary role in the stories of his much more celebrated successor Bayinnaung.

One of the first modern novels published in the Burmese language in the early 20th century was a fictional recreation of his reign named Tabinshwehti Wuttu Daw Gyi.