[5] In the following years, Toungoo used the newly acquired kingdom's wealth and manpower to reunify the various petty states that had existed since the fall of Pagan Empire in 1287.

Circa 1494, Toungoo, then still a vassal of Ava, raided Hanthawaddy's territory, taking advantage of the larger kingdom's succession crisis.

When Ava fell to the combined forces of the Confederation and Prome in 1527, many people fled to Toungoo, the only region in Upper Burma at peace.

War arrived uncomfortably close to Toungoo in 1532–1533 when the Confederation of Shan States, already ruling much of Upper Burma, attacked its erstwhile ally Prome, and sacked the city.

Unlike Prome, which sits on the Irrawaddy river, Toungoo was tucked away behind the Pegu Yoma range and was not connected to Upper Burma by any major water way, presenting a difficult logistical challenge for potential invaders.

Takayutpi's brother-in-law Saw Binnya practically ruled Martaban region like a sovereign, and scarcely acknowledged the high king at Pegu (Bago).

In each campaign, Toungoo armies had only 6000 to 7000 men, a few hundred cavalry, and a few dozen war elephants and did not yet have access to foreign troops or firearms.

The direct route from Pegu to Prome, though much shorter, involved crossing the Bago Yoma range, and was not practical for large armies.

They knew that a large body of enemy inside walls with better leadership would pose a major problem for their tenuous hold on Lower Burma.

[12] Bayinnaung's light troops caught up with the main Hanthawaddy armies led by Gen. Binnya Dala and Gen. Minye Aung Naing near Naungyo in the Irrawaddy delta.

Toungoo retreated but soon gained the allegiance of many Mon lords, and manpower after Hanthawaddy's king Takayutpi died a few months later.

He had fortified the wealthy port, and enlisted Portuguese mercenaries and seven warships led by Paulo de Seixas, guarded the harbor.

[18] Toungoo forces now included 700 Portuguese mercenaries led by João Caeiro (Joano Cayeyro) who brought light artillery and muskets.

Saw Binnya finally offered to surrender provided that he be allowed to remain viceroy in exchange for an annual tribute of 30,000 viss (48,987.9 kg) of silver bullion and other valuable presents.

Then the rafts with mounted bamboo towers, crammed with troops and musketeers, slipped past the wreckage, and made it to the wall by the harbor.

The governors of Moulmein (Mawlaymyaing) and southern territories (present-day Mon State), abutting then Siamese frontier submitted.

Toungoo's victory gave the upstart kingdom complete control of coastal Lower Burma's manpower, access to foreign firearms and maritime wealth to pay for them.

[23][24] Toungoo kings would leverage these newfound assets for further expansions in the remainder of the century, and build the largest empire in the history of Southeast Asia.

Moreover, Toungoo's 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 rise of Burman culture and Burmese language in the Irrawaddy valley.