In late 1875, Sioux and Cheyenne Indians defiantly left their reservations, outraged over the continued intrusions of whites into their sacred lands in the Black Hills. They gathered in Montana with the great warrior Sitting Bull to fight for their lands. The following spring, two victories over the US Cavalry emboldened them to fight on in the summer of 1876.
To force the large Indian army back to the reservations, the Army dispatched three columns to attack in coordinated fashion, one of which contained Lt. Colonel George Custer and the Seventh Cavalry. Spotting the Sioux village about fifteen miles away along the Rosebud River on June 25, Custer also found a nearby group of about forty warriors. Ignoring orders to wait, he decided to attack before they could alert the main party. He did not realize that the number of warriors in the village numbered three times his strength. Dividing his forces in three, Custer sent troops under Captain Frederick Benteen to prevent their escape through the upper valley of the Little Bighorn River. Major Marcus Reno was to pursue the group, cross the river, and charge the Indian village in a coordinated effort with the remaining troops under his command. He hoped to strike the Indian encampment at the northern and southern ends simultaneously, but made this decision without knowing what kind of terrain he would have to cross before making his assault. He belatedly discovered that he would have to negotiate a maze of bluffs and ravines to attack.