Sitting Bull did not agree to the treaty. He told the Jesuit missionary, Pierre Jean De Smet, who sought him out on behalf of the government: "I wish all to know that I do not propose to sell any part of my country." He continued his hit-and-run attacks on forts in the upper Missouri area throughout the late 1860s and early 1870s. The events of 1866–1868 mark a historically debated period of Sitting Bull's life. According to historian Stanley Vestal, who conducted interviews with surviving Hunkpapa in 1930, Sitting Bull was made "Supreme Chief of the whole Sioux Nation" at this time.
Sitting Bull encroachment and the depletion of buffalo herds reduced their resources and challenged Native American independence. In 1875, the Northern Cheyenne, Hunkpapa, Oglala, Sans Arc, and Minneconjou camped together for a Sun Dance, with both the Cheyenne medicine man White Bull or Ice and Sitting Bull in association. This ceremonial alliance preceded their fighting together in 1876. Sitting Bull had a major revelation. At the climactic moment, "Sitting Bull intoned, 'The Great Spirit has given our enemies to us. We are to destroy them. We do not know who they are. They may be soldiers.' Ice too observed, 'No one then