The Baro-Bhuyans (or Baro-Bhuyan Raj; also Baro-Bhuians and Baro-Bhuiyans) were confederacies of soldier-landowners in Assam and Bengal in the late Middle Ages and the early modern period. The confederacies consisted of loosely independent entities, each led by a warrior chief or a landlord (zamindars). The tradition of Baro-Bhuyan is peculiar to both Assam and Bengal and differ from the tradition of Bhuihar of Uttar Pradesh and Bihar—in Assam this phenomenon came into prominence in the 13th century when they resisted the invasion of Ghiyasuddin Iwaj Shah and in Bengal when they resisted Mughal rule in the 16th century. Baro denotes the number twelve, but in general there were more than twelve chiefs or landlords, and the word baro meant many. Thus, Bhuyan-raj denoted individual Bhuyanship, whereas Baro-Bhuyan denoted temporary confederacies that they formed. In times of aggression by external powers, they generally cooperated in defending and expelling the aggressor. In times of peace, they maintained their respective sovereignty. In the presence of a strong king, they offered their allegiance. In general each of them were in control of a group of villages, called , and the more powerful among them called themselves raja. The rulers of the Bhuyanships belonged to different ethnic, religious or social backgrounds. In 13th century Brahmaputra valley the system of Baro-Bhuyan Raj (confederacy) was formed from the petty chieftains—the remaining fragments of the erstwhile Kamarupa state. They often resisted foreign invasions (Ghiyasuddin Iwaj Shah in the 13th century), removed foreign rule (Hussain Shah in the 16th century) and sometimes usurped state power (Arimatta in the 14th century). They occupied the region west of the Kachari kingdom in the south bank of the Brahmaputra river, and west of the Chutiya kingdom in the north bank. These included areas of Nagaon, Darrang and Sonitpur districts. Subsequently, the Baro Bhuyan rules ended in the 16th century as they were squeezed between the Kachari kingdom and the Kamata kingdom in the west and were slowly overpowered by the expanding Ahom kingdom in the east. In Bengal, the most prominent Baro-Bhuyan confederacy was led by Isa Khan of Sonargaon in the 16th century, which emerged during the disintegration of the Bengal Sultanate in the region, as a resistance to the Mughal expansion. They carved the land of Bhati and other areas of Bengal into twelve administrative units or Dwadas Bangla. The Baro-Bhuyans gradually succumbed to the Mughal dominance and eventually lost