The Great Sioux War (1876-1877) was a conflict between the United States and several Native American tribes, primarily the Sioux Nation. The war was sparked by the U.S. government's desire to expand into the Black Hills of South Dakota, an area sacred to the Sioux, especially after gold was discovered there. Tensions escalated as the U.S. sought to force the Sioux onto reservations. Key battles during the war included the Battle of Little Bighorn, where General George Custer and his troops were defeated by a coalition of Sioux and Cheyenne warriors. The war ultimately ended with the U.S. military's victory, leading to the forced relocation of the Sioux and the signing of treaties that significantly reduced their land.