The U.S. government has continued to punish the Sioux in the aftermath of the Dakota War of 1862, including those who had not participated in the war.
Large military expeditions into Dakota Territory in 1863 had pushed most of the Sioux to the western side of the Missouri River at least temporarily and made safer, although not entirely safe, the frontier of white settlement in Minnesota and the Dakotas.
Four whites are killed by Sioux raiders in the spring of 1864.
An important impetus to another military campaign against the Sioux is the desire to protect lines of communication with recently discovered goldfields in Montana and Idaho.
The lifeline for the American gold miners are steamboats plying the Missouri River through the heart of Sioux territory.
During the winter of 1863-1864, Major General John Pope had ordered Brigadier General Alfred Sully to establish several forts along the Missouri River and in the eastern Dakotas to secure the communication routes to the goldfields and to eliminate the Sioux threat to the settlers east of the Missouri River.
Sully’s First Brigade, consisting of up to seventeen hundred men, follows the Missouri River from its starting point at Sioux City, Iowa.
The Second Brigade with about fifteen hundred and fifty men marches overland from Fort Ridgely in Minnesota.
On the march up the Missouri, the Sioux kill one soldier and wound another.
The three Sioux perpetrators are caught, killed, and decapitated.
Additional soldiers and civilians with fifteen steamboats chug up the Missouri River to support the army on the ground.
Sully’s two columns of soldiers unite on June 29.
