This is an ethnographic study on the Tay ethnic identity and their incorporation into the modern nation-state of Vietnam, mainly focused on the local history of the Tay villages in Mai Chau, Hoa Binh Province. This study includes oral histories of the local Tay people and their contact with others, since their settlement in the Mai Chau valley about seven centuries ago, such as aboriginal hill tribes, Chinese invaders, French colonialists, Vietnamese revolutionary state, ethnic majorities or the Kinh, and other ethnic groups. However, the main parts of the paper contains the various stories of turbulent times, since 1940s, of revolution, war and the building of the Democratic Republic of Vietnam. This study shows that the process of becoming part of the modern nation-state of Vietnam as national minorities involves both fixed and self-confining of the Tay. They have been confined and fixed by the state and powerful others through the ethnic classification project, collectivisation policies, and ritual reform. Yet their lives and identity have also constructed and self-confined by Tay people themselves in the dynamic contexts of historical process. They were already settled in the Mai Chau valley and living with wet-rice cultivation before the Vietnamese government came along. Also, they have had a hierarchical society and political relations among themselves for long time based on their own class structure.