Answer:
They were forced into reservation
Step-by-step explanation:
At that time, herding buffalos was the main source of living for the Indian tribes of the great plains. This help them survive without having to sell their lands to the government.
After the buffalo were hunted to near extinction, It is extremely difficult for members of the native tribes to find a source of living to feed the members of their community. This made them have no choice but to accept the government's offer and got into the reservation.