Binnya U, descendant of the Thai chief Wareru, had established Hanthawaddy as the capital of the Mon Hanthawaddy Kingdom, which covers all of what is now Lower Burma.

In 1519, António Correia, then a merchant from the Portuguese casados settlement at Cochin, had landed in Bago, then known to the Portuguese as Pegu, looking for new markets for pepper from Cochin.

A year later, Portuguese India Governor Diogo Lopes de Sequeira had sent an ambassador to Pegu.

Tabinshwehti and his court had selected Hanthawaddy as their first target because its king, Takayutpi, is a weak leader who does not command respect of his vassals.

Takayutpi's brother-in-law Saw Binnya practically rules the Martaban region as a sovereign, and scarcely acknowledges the high king at Pegu.

Takayutpi in turn makes an alliance with the Prome Kingdom, a vassal of the Confederation of Shan States.

Toungoo's opening maneuvers amounted to a mere raids of Hanthawaddy territory: its initial dry-season raids in 1534–1535, 1535–1536, and 1536–1537 have all failed against Pegu's fortified defenses, aided by foreign mercenaries and firearms.

In each campaign, Toungoo armies have only six thousand to seven thousand men, a few hundred cavalry and a few dozen war elephants, and do not yet have access to foreign troops and firearms.

Unlike his father Binnya Ran II, Takayutpi cannot organize any retaliatory actions.

His nominal subordinates in the Irrawaddy delta and Martaban send no aid.

Nonetheless, Pegu's defenses, led by two leading ministers of the court, Binnya Law and Binnya Kyan, have withstood the raids.