An ex-Buddhist monk, and a son of King Binnya Ran II by a minor queen, Htaw first raised a rebellion in 1549 during the reign of King Tabinshwehti of Toungoo, who had conquered the Mon-speaking kingdom ten years earlier.
Htaw was on the run in the delta chased after by Gen. Bayinnaung of Toungoo when Tabinshwehti was assassinated by one of his close advisers, Smim Sawhtut, on 30 April 1550.
Htaw raised an army and defeated Sawhtut near Pegu (Bago) in August 1550.
In desperation, Htaw challenged and fought Bayinnaung in single combat, both on their war elephants.
Bayinnaung was victorious, charging his foe and driving him off after breaking the tusk of Htaw's elephant.