General George Crook advanced north from Fort Fetterman with nearly a thousand cavalry and mule-mounted infantry, confident in his reputation as an Indian fighter. His Crow and Shoshoni allies had warned him that the Lakota and Cheyenne were "as numerous as grass," but Crook pressed on. Among his column rode an unusual figure: Calamity Jane, disguised as a male teamster. On June 16, Crook left his wagon train behind and pushed toward the Rosebud with four days' rations and 100 rounds per soldier. His Indian allies spoiled any chance of surprise when they encountered a buffalo herd and opened fire. Unknown to Crook, nearly a thousand warriors had ridden out from their village the night before, crossing the miles to meet him.

At 8 a.m. on June 17, Crook's exhausted troops halted to rest along Rosebud Creek. The Crow and Shoshoni scouts remained alert while soldiers dozed in their marching order. Then gunfire erupted from the bluffs. Two Crow scouts galloped into camp shouting "Lakota! Lakota!" The fighting that followed would sprawl across three miles of broken terrain for six hours. Captain Anson Mills later described the warriors: "They were the best cavalry soldiers on earth. In charging up toward us they exposed little of their person, hanging on with one arm around the neck and one leg over the horse, firing and lancing from underneath the horses' necks." Crazy Horse led charges and countercharges, drawing the soldiers deeper into the rough country.

During Mills' cavalry charge, a Cheyenne warrior named Comes in Sight lost his horse to gunfire. Stranded on foot with soldiers bearing down, death seemed certain. Then his sister Buffalo Calf Road Woman galloped through the battle smoke, and Comes in Sight swung onto her horse. The two escaped together. For the Cheyenne, this act of courage defined the entire engagement. Lieutenant Colonel William Royall's command, meanwhile, found itself in desperate straits. Separated from Crook by the valley of Kollmar Creek, Royall's six cavalry companies faced attacks on three sides. Only the timely intervention of the Crow and Shoshoni scouts prevented his destruction.

By 2:30 p.m., Mills' unexpected appearance on the Lakota flank caused the warriors to break contact and withdraw. Crook claimed victory by virtue of holding the field, but his actions told a different story. He had expended between 10,000 and 25,000 rounds of ammunition with minimal enemy casualties. Concerned for his wounded and short on supplies, Crook retreated to Goose Creek near present-day Sheridan, Wyoming, where he would remain immobile for seven weeks awaiting reinforcements. His absence from the campaign meant that eight days later, when Lieutenant Colonel George Custer led the 7th Cavalry into the Little Bighorn Valley, Crook's column was nowhere close to provide support.

The Battle of the Rosebud demonstrated that the Lakota and Cheyenne under leaders like Crazy Horse would not follow the usual Plains Indian tactics of quick raids and ambushes. They would stand and fight. The U.S. Army had planned a three-pronged convergence on the hostile bands. Colonel John Gibbon advanced from the west; General Alfred Terry with Custer came from the east; Crook pushed north. The Rosebud broke that plan. What happened eight days later at Little Bighorn might have unfolded differently if Crook's thousand soldiers had been present instead of sitting idle at Goose Creek, nursing their wounds and waiting for reinforcements that would arrive too late to matter.