In August 1862 the Dakota of Eastern Sioux resorted to armed conflict against the white settlers of southern Minnesota. This study uses an ethnohistorical approach to explain why the bonds of peace between the Dakota and the whites were suddenly broken. It shows how the Dakota concept of kinsmen affected the tribe's complex relationships with the whites. The Dakota were obliged to help their relatives by any means possible. Traders who were adopted or married into the tribe gained from this relationship, but had reciprocal responsibilities. After the 1820s, the trade in furs declined, more whites moved into the territory, and the Dakota became more economically dependent on the whites. When American officials and traders failed to fulfill their obligations, many Dakotas finally saw the whites as enemies to be driven from Minnesota. This edition includes a new introduction by the author, who comments on scholarly developments in the field of ethnohistory in the 19th century.