 Complete the following phrase:  After the Civil War, population expansion, railroad construction, and the disappearance of the buffalo herds heightened military tensions on the Great Plains. Several tribes, especially the Sioux and Comanche, fiercely resisted confinement to reservations. The main role of the Army was to keep indigenous peoples on reservations and to end their wars against settlers and each other, William Tecumseh Sherman and Philip Sheridan were in charge. A famous victory for the Plains Nations was the 