He served over 67 years as a senior royal army officer and court minister under seven kings of Ava from Minkhaung I to Narapati I.
Near the end of the ensuing civil war in 1426, Yazathingyan, in a rare break with his brother, switched sides, and became the chief minister of the incoming power, Gov.
The chief minister fully backed Thado's successor King Minye Kyawswa's policy to forcefully regain the vassal states in revolt.
When Minye Kyawswa died without a male heir in 1442, Yazathingyan felt powerful enough to offer the throne to the late king's brother-in-law Gov.
[note 6] In 1425, Yazathingyan and Gamani decided to side with the usurpers Prince Nyo of Kale and Queen Shin Bo-Me, following the assassinations of Thihathu and his son and successor Min Hla.
[8][9] However, they faced a serious challenger in Sawbwa Thado of Mohnyin, who vehemently opposed Nyo's takeover, and went on to declare war on the Ava regime in February 1426.
[note 7] The brothers—along with their youngest army commander brother Yan-Lo Kywe—remained by the royal couple into early May even as Thado's forces closed in, and other vassals deserted.
[11][12] By mid-May, however, Yazathingyan and Yan-Lo Kywe too were wavering; they refused to go along with Gamani's plan to evacuate the couple out of Ava.
Gamani would remain in prison until late 1427 when he was asked to defend the capital region from Kyawhtin's rapidly advancing forces.
He advised Thado to focus on consolidating the core Irrawaddy valley, and extending control to closer southeastern districts of Pinle, Yamethin and Toungoo.
In 1429, upon Yazathingyan's recommendation, the king appointed his second son Thihathu as viceroy of Prome (Pyay) in the south, and his younger brother Nawrahta as governor of Myedu in the north, in order to defend the core region along the Irrawaddy.
In 1428, upon Yazathingyan's advice, Thado sent two separate missions to Onbaung and Yat Sauk Naung Mun, asking Onbaung to withdraw its support of Prince Minye Kyawhtin at Pinle, and Yat Sauk to end its support of Thinkhaya III of Toungoo, in exchange for Ava's recognition of the Shan states.
[21][22] Yazathingyan gave a similar advice in 1430 when the combined forces of the southern Hanthawaddy Kingdom and the rebel state of Toungoo laid siege to Prome.
[25][26] Yazathingyan was aghast when Thado famously responded to Binnya Ran's 1436 takeover of Toungoo, by ordering the recalibration of the Burmese calendar.
[26][28] Yazathingyan fully supported the new king Minye Kyawswa's policy to forcefully reclaim Ava's former vassals.
The campaign, initially led by the king's uncle Nawrahta I of Myedu, got off to a poor start, and turned around only after Gamani and Yazathingyan took over the overall command.
[31]) Because Thihapate at the time was laying siege to Mogaung, 500 km north of Ava, the ministers rushed a messenger on horseback, offering him the throne.
[40][41] In 1455, Yazathingyan advised Narapati to sign a peace treaty with King Min Khayi of Mrauk-U (Arakan).
At Prome, he and his son tended to the royal couple until they were forced to flee back to Ava by Thado Minsaw,[47] who thought the father-son duo had too much influence over his parents.