Founded as the de jure successor state of the Pagan Empire by Thihathu, Pinya faced internal divisions from the start.

The rump Pinya Kingdom was left embroiled in an intense rivalry between Thihathu's other sons Uzana I and Kyawswa I until 1344.

In the 1350s, Kyawswa II repaired Pinya's long-strained relationship with Sagaing, in order to face off against the northern Shan state of Maw.

Although its successor Ava would prove more successful in reassembling major parts of the erstwhile empire, it too would be hampered by fierce regional rivalries, and Myanmar would remain divided into the mid-16th century.

Pinya was the successor state of Myinsaing, the polity that succeeded the Pagan Empire in Upper Burma.

Various Shan states, nominal Mongol vassals, now dominated the entire northwestern-to-southeastern arc surrounding the Irrawaddy valley.

Thihathu, the youngest and most ambitious brother, was never satisfied with a mere regent status, and declared himself king in 1309.

To commemorate his reign, Thihathu founded a new capital at Pinya, also in the Kyaukse valley but closer to the Irrawaddy.

[7] For the first time since the 1280s, the entire Irrawaddy valley between Prome in the south and Tagaung in the north was under a single ruler.

The Myinsaing-Pinya rulers had inherited the longstanding problem that had existed since the late Pagan period: between one and two-thirds of Upper Burma's cultivated land had been donated to religion, and the crown had lost resources needed to retain the loyalty of courtiers and military servicemen.

[8] Furthermore, "markedly drier weather during the late 13th and much of the 14th centuries" in Upper Burma forced large migrations from the established granaries (Kyaukse, Minbu, and Mu valley)[9] "to better watered districts farther south".

The king allowed Saw Yun to remain in office at Sagaing in exchange for his son's nominal submission.

He successfully reunified Pinya's military corps in Central Burma, and formed elite cavalry and shielded infantry units.

[29] Similarly, his attempt to check the power of the Buddhist clergy was not successful, not least because the court did not fully cooperate.

[note 7] A key driver for the truce may have been the emergence of the Shan state of Maw (Mong Mao), which had fought a successful war against its Mongol overlords (1342–48).

[32] After Maw reached a deal with the Mongols in 1355,[32] they turned their attention to their south, launching their first raid into Sagaing territory in 1356.

Recognizing the eventual threat to his own realm farther south, Kyawswa II in 1357/58 agreed to an alliance with Sagaing.

[34] Kyawswa II had no response as the Maw forces broke through the Sagaing lines and breached Pinya territory in early 1359.

[37] At Sagaing, a young prince named Thado Minbya (r. 1364–67), a great grandson of Thihathu, seized the throne.

[38] Over the next six months, he feverishly built a new citadel at a more strategic location at the confluence of the Irrawaddy and the Myitnge in order to defend against the Maw raids.

On 26 February 1365, the king proclaimed the foundation of the city of Ava (Inwa), as the capital of the successor state of Pinya and Sagaing kingdoms.

[40][41] The court, Hluttaw, was the center of administration, representing at once executive, legislative and judiciary branches of the government.

[42] The court administered the kingdom at three general levels: taing (တိုင်း, province), myo (မြို့, town), and ywa (ရွာ, village).

[43] Unlike the Pagan government, the Pinya court's reach was limited mainly to the Kyaukse region and its vicinity.

Other vassal states listed in the chronicles were Pindale, Pyinzi, Yindaw, Hlaingdet, Kyaukpadaung, Pahtanago, Mindon, Taingda, Mindat, Kanyin, Myaung, Myede, Salin, Paunglaung, Legaing, Salay, Kugan Gyi, Kugan Nge, Ywatha, Talok, Ten tracts of Bangyi, Yaw, Htilin, Laungshay, and Tharrawaddy.

[19] Kyawswa I reunified the army but later Pinya kings never controlled a large enough force to make a difference.

[note 10] Most royal chronicles treat Myinsaing-Pinya as a single period, and Sagaing as a junior branch of the Myinsaing dynasty.