The Cheyenne were an Indian tribe that occupied much of the Confederation of Vandalia in the early 19th century. Following the outbreak of the Rocky Mountain War in 1845 between the Confederation of North America and the United States of Mexico, the Cheyenne living north of the Arkansas River sided with the Mexicans. Under their War Chief Running Deer, these southern Cheyenne withdrew across the Rocky Mountains to Mexico del Norte, where they engaged in a series of battles with the North Americans in alliance with the Mexican army. The most notable of these were the Battle of Arroyo de Dios, in which General Philip Lodge lost 10,000 men, and the Battle of Arroyo de Quatros Hombres, in which Running Deer defeated General Harry Chapin. Although Sobel makes no further mention of the Cheyenne, presumably the southern Cheyenne under Running Deer remained in Mexico del Norte after the war.