In this compelling portrait of interracial activism, Mark A. Lause documents the efforts of radical followers of John Brown to construct a triracial portion of the Federal Army of the Frontier. Mobilized and inspired by the idea of a Union that would benefit all, black, Indian, and white soldiers fought side by side, achieving remarkable successes in the field. Against a backdrop of idealism, racism, greed, and the agonies and deprivations of combat, Lause examines links between radicalism and reform, on the one hand, and racialized interactions among blacks, Indians, and whites, on the other. Lause examines how this multiracial vision of American society developed on the Western frontier. Focusing on the men and women who supported Brown in territorial Kansas, Lause examines the impact of abolitionist sentiment on relations with Indians and the crucial role of nonwhites in the conflict. Through this experience, Indians, blacks, and whites began to see their destinies as interdependent, and Lause discusses the radicalizing impact of this triracial Unionism upon the military course of the war in the upper Trans-Mississippi. The aftermath of the Civil War destroyed much of the memory of the war in the West, particularly in the Indian Territory (now Oklahoma). The opportunity for an interracial society was quashed by the government's willingness to redefine the lucrative field of Indian exploitation for military and civilian officials and contractors. Assessing the social interrelations, ramifications, and military impact of nonwhites in the Union forces, Race and Radicalism in the Union Army explores the extent of interracial thought and activity among Americans in this period and greatly expands the historical narrative on the Civil War in the West.