About two-thirds of western tribal groups live on the Great Plains.These nomadic tribes, such as the Sioux, Blackfoot, Cheyenne, Crow, and Comanche, gave up farming in colonial times after the introduction of the horse by the Spanish. By the 1700s, they had become skillful horsemen and developed a way of life centered on the hunting of buffalo. Although they belong to tribes of several thousand, they live in smaller bands of 300–500 members. Their conflicts with the U.S. government are partly the result of white Americans having little understanding of the Plains people’s loose tribal organization and nomadic lifestyle.President Andrew Jackson’s policy of removing eastern Native Americans to the West is based on the belief that lands west of the Mississippi would permanently remain “Indian country.” This expectation soon proved false, as wagon trains rolled westward on the Oregon Trail, and plans were made for building a transcontinental railroad. In 1851, in councils at Fort Laramie and Fort Atkinson, the federal government began to assign the plains tribes large tracts of land—or reservations— with definite boundaries. Most Plains tribes, however, refused to restrict their movements to the reservations and continued to follow the migrating buffalo wherever they roamed. As thousands of miners, cattlemen, and homesteaders began to settle on Native American lands, conflict sprouted.In 1864, the Colorado militia massacred an encampment of Cheyenne women, children, and men at Sand Creek, Colorado. In 1866, during the Sioux War, the tables were turned when an army column under Captain William Fetterman was wiped out by Sioux warriors. Following these wars, another round of treaties attempted to isolate the Native Americans of the Plains on smaller reservations with promises of government support to be provided by federal agents. However, gold miners refused to stay off Native Americans’ lands if gold was to be found on them, as indeed it was in the Dakota’s Black Hills. Soon, minor chiefs not involved in the treaty-making and younger warriors denounced the treaties and tried to return to ancestral lands. A new round of conflicts in the West began. There was the Red River War against the Comanche and a second Sioux War led by Sitting Bull and Crazy Horse. Before the Sioux went down to defeat, they ambushed and destroyed Colonel George Custer’s command at Little Big Horn.Chief Joseph’s courageous effort to lead a band of the Nez Perce´ into Canada ended in defeat and surrender. The constant pressure of the U.S. Army forced tribe after tribe to comply with Washington’s terms. In addition, the slaughter of most of the buffalo will doom the way of life of the Plains people.