On July 28, 1864, a U.S. military force commanded by General Alfred Sully attacked several groups of the Dakota, Nakota, and Lakota (Sioux) Nations camped at Killdeer Mountain. Major Sioux leaders included Medicine Bear and Sitting Bull. Sully's force had been sent into Dakota Territory to punish those who had participated in Minnesota's Dakota Conflict of 1862 and to develop routes to western gold fields. Many of the Sioux groups gathered there had not participated in the Dakota Conflict and had sought to make peace with the government. Equipped with several cannons, Sully's force attacked and shelled the encampment, causing warriors as well as unarmed men, women, and children to flee into the Little Missouri badlands. Native American oral tradition says that many escaped through an opening at the top of Killdeer Mountain known as the Medicine Hole. Sully estimated that between 100 and 150 Sioux were killed, though the exact number is unknown, and his troops suffered five deaths. Sully's men destroyed the Sioux lodges and all their winter supplies, then moved west across the badlands to Fort Union, skirmishing during the march with many of the warriors they had faced there. The conflict further embittered relations between many Northern Plains tribes and the U.S. government, and Sully's campaign, culminating at Killdeer Mountain, was a prelude to the Sioux Wars of the 1870s.