The Sutiya Kingdom was established by Birpal in 1187 in northeastern Assam and some areas of present day Arunachal Pradesh, with the capital at Sadiya. The Sutiya are an indigenous ethnic group that spoke a Tibeto-Burman language, but now they speak Assamese language. According to tradition, Birpal at first became the chief of sixty families.
The most illustrious of the Sutiya kings was Gauri Narayan (Ratnadhwajpal), son of Birpal. He brought many other Sutiya groups into his kingdom. In 1224 Ratnadhwajpal defeated Bhadrasena, the king of Swetagiri. Then he went on to subjugate Nyayapal and marched toward Kamatapur, where he formed an alliance with the Kamata ruler by marrying a princess. Then he marched to Dhaka, and camped some distance away from the city. Though records exist of this expedition, there is no account of a war at Dhaka.
The hostilities with the Ahoms began in 1376 when the Ahom king, Sutuphaa, was killed by the Sutiya king during a friendly encounter. The simmering dispute often flared till 1522 when the Ahoms finally took Sadiya and killed the then king Nityapal and the queen Sadhani preferring death to dishonour committed suicide by jumping from the top of a hill. The Ahoms established their rule by instituting the position of Sadiyakhowa Gohain, the governor in charge of Sadiya. But the Sutiya had dispersed to frontier regions, and continued raids against the Ahoms.
The Sutiyas are one of the major section of the plain inhabitants of Assam. They belong to the great Mongoloid Stock. Lingustically however they belong to the Tibeto-Burman family. They had established their own kingdom comprising some areas of present day Arunachal Pradesh and upper Assam districts with Kundill and Sadiya as capitals. The former kingdom of the Sutiyas well known as Vidarbha and its capital was situated at Kundill. The seat of the Sutiyas when they were in the ascendant, appears to have been about Lakhimpur and the back of the Subansiri River. They hold all the countries to the north of Brahmaputra probably as far down as Biswanath.
The Sutiyas have been divided into a number of groups viz. the Deuri Sutiyas,the Hindu Sutiyas,Miri Sutiyas,the Naga Sutiyas etc. The Deuris are at present recognised as one of the plain tribes of Assam.