The war's origins can be traced to Hanthawaddy Pegu's political turmoil, which intensified after King Razadarit's rise to power in 1384 through a rebellion against his ailing father.

Governor Smin Sam Lek of Donwun and Viceroys Laukpya of Myaungmya and Byattaba of Martaban refused to recognize the new king.

[3] In the first phase, Swa Saw Ke of Ava began the hostilities by invading Pegu during the latter kingdom's dynastic succession struggles.

Both land and naval forces laid siege to a newly reinforced set of Peguan forts in Hmawbi, Hlaing, Dagon and Dala.

After a swift attack on Governor Nyi Kan-Kaung's garrison in Dala, Razadrit advanced to Bassein where, despite several charges, he was unable to break past the defensives or Laukpya's war boats on the Pathein River.

Swa could not overlook this latest transgression and, finally freed up from the war with Maw, ordered a renewed campaign to the south.

After one Peguan squadron, led by Maha Thamun, got close enough to Swa's royal war boat, Ava called off the attacks.

[6] Pegu's new young king Razadarit aided by able commanders Byat Za, Dein Mani-Yut, Lagun Ein and Maha Thamun had defeated Ava's multiple invasions.

To take advantage of Ava's dynastic succession crisis, Razadarit invaded Upper Burma in full force with a large flotilla in 1401.

The second truce lasted less than five years as Ava quickly went on an expansion spree, swallowing up the Shan states of Kale and Mohnyin in the north, and Launggyet Kingdom (Arakan) in the west, between 1404 and 1406.

Pegu's Crown Prince Binnya Ran I made peace with Ava by giving his elder sister Shin Sawbu to Thihathu.