About the middle of last century the Siamese made an attack on the Trans-Salween State of Kengtung. The Cis-Salween States were called upon for contingents to form a force to repel the invasion, and Sang Hai, who was previously unknown, led the Hsenwi men to victory and won much renown. On his return, finding himself at the head of victorious troops, he rebelled against his lawful ruler Naw Hpa, and turned him out.
Naw Hpa was summoned to Mandalay, and condemned to imprisonment for having failed to maintain his authority, while a cadet of the Hsenwi house was appointed in his stead. This cadet, U Po by name, was driven away ignominiously by Sang Hai, and was recalled to Mandalay and sent to join Naw Hpa in jail. Numerous Burmese officials of high rank with imposing titles were sent up one after another, and one after another was expelled by Sang Hai, and they came back, in the order of their going, to join the company of failures in Mandalay prison.
At last, about 1877, all the Sawbwas from Yawnghwè to Möng Löng were ordered to make a combined attack on Sang Hai. This was too much for the usurper. He went east of the Salween, and Naw Hpa was sent back to rule a ruined and distracted country. But Sang Hai before he retired had thrown his mantle over the shoulders of his son-in-law, San Ton Hon, who was for a Shan a good fighting-man. The unlucky Naw Hpa was driven out once more, and again ordered to Mandalay to explain his failure to hold his own. He knew by experience what this meant, and deputed his son, who was known as the Naw Möng, to represent him at Court, or rather in prison, while he himself took refuge with the Kachins.
When Thebaw succeeded his father Mindon, he imprisoned his stepmother, the Hsenwi Queen, Naw Hpa's daughter, and killed her son. And as Naw Hpa himself was a refugee and Naw Möng was in jail San Ton Hon was left free to establish himself in Hsenwi, or rather in the Northern and Eastern Divisions of the State. The Southern, known as the Taunglet, had already broken away and separated into four petty chiefships. The middle portion, called the Alelet, was governed in a fashion by Sang Aw, commonly know as the Pa-ôk-Chok, who had his headquarters at Möngyai. A Burmese official with a small force had been left at Lashio, but unable to support himself against San Ton Hon he withdrew as soon as he heard of the fall of the Monarchy.