The issue of separate state had become an election issue in 1957 general elections in Assam. The EITU, United Mizo Freedom Organization(UMFO), the Mizo Union, and the Garo National Union captured majority of seats giving the impetus and popular mandate for the Hills movement, while the Congress lost—all five seats in the United Khasi-Jaintia Hills, three seats in Garo Hills, and one seat in Mikir Hills and North Cachar Hills. Bimala Prasad Chaliha with confidence from hills people, became the Chief Minister of Assam. In 1957, Sangma was elected to Assam Legislative Assembly. In the following year, he joined the cabinet of Assam to look after the departments of tribal regions, information, publicity, and transport. After the Indian independence, when the Nagas declared war against India, the tribes inhabiting the Khasi-Jhantia-Garo Hills extended co-operation to Government of Assam; as a result, Williamson Sangma was taken in the cabinet of Chaliha, Chief Minister of Assam, as a Cabinet minister in charge of the Tribal Areas Department. When the Assamese language bill was passed in spite of opposition from tribal people later, he resigned from the cabinet to fight for the cause of separate statehood.