Until August 18, summer emigration in 1854 appears to have been unaffected by trouble with the Indians. On that day a Mormon caravan passed a village of Brule Sioux 8 miles east of Fort Laramie, and a cow ran into the village where it was appropriated by a visiting Miniconjou brave. This matter was reported at the fort by both the Mormons and the chief of the Brules. Lt. John Grattan, Sixth Infantry, with 29 soldiers, 2 cannon, and an interpreter, was dispatched to the village to arrest the offending Indian. Unfortunately, the interpreter was drunk and the young officer was arrogant. The Indian offender refused to give himself up and a fight was precipitated in the Indian village, resulting in the annihilation of the military party.

The enraged Indians then pillaged Bordeaux’s nearby trading post and helped themselves to both annuity goods and company property at the American Fur Co.’s post 3 miles up the river. Fortunately, no attack was made on the small remaining garrison of Fort Laramie to which neighboring traders and others rushed for protection. All Sioux immediately left the vicinity of the fort, and the Cheyennes and Arapahoes waited only for the distribution of treaty goods before moving away.

During the following year, Indians committed many small-scale depredations along the Oregon Trail. However, despite greatly exaggerated alarms, the emigrants of 1855 were for the most part unmolested. Meanwhile, the Army had become convinced that the Indians must be punished, and a force of 600 men under Gen. W. S. Harney marched westward from Fort Leavenworth. The Indian agent at Fort Laramie warned all friendly Indians to come to the south side of the Platte—a warning heeded by many bands. On September 2, General Harney arrived at Ash Hollow, 150 miles below Fort Laramie, and located Little Thunder’s band of Brule Sioux some 6 miles north on the Blue Water. Early the next morning, after rejecting protestations of friendship by Little Thunder, his troops attacked the village from two sides, killing 86 Indians and capturing an almost equal number of women and children. At Fort Laramie, General Harney issued a stern warning to other Sioux bands, then proceeded overland through Sioux territory to establish a military post at Fort Pierre on the upper Missouri River.