The answer to this question can be found in Chapter 19 of A People’s History of the United States. This chapter is entitled “Surprises.” The brief answer is that, according to Howard Zinn, the white people of the United States had felt that the Native Americans had been oppressed so much that they “would not be heard from again.”
In this chapter, Zinn argues that the American government and people had badly oppressed Native Americans through the years. He claims that white Americans would have believed that this oppression had broken the spirits of the Indians. He says, for example, that, the Native Americans, having been
pushed back and annihilated by the white invaders, would not be heard from again.
Later, he says that people thought that the Navajo “would not be heard from again” because their villages had been burned and their crops destroyed. By saying this, Zinn is implying that whites felt that they had managed to completely break the Indians to the point where they would never stand up for themselves. Zinn then argues that the Indian movement was a major surprise to whites because the Indians were resilient enough to continue to fight for their rights even though they had been so terribly oppressed.