Between the War of 1812 and the Civil War, General William S. Harney became one of the best-known military figures in America. In a career aided by Andrew Jackson and the concept of an expansible army, Harney saw duty in virtually every part of the country and participated in most of the key military episodes of his time. He chased remnants of Lafitte pirates in Louisiana, campaigned with Abraham Lincoln and Zachary Taylor during the Black Hawk War, developed Vietnam-style riverine tactics that ended the Second Seminole War, and led Winfield Scott's cavalry in the Mexican War. In the 1850s Harney devised the army's largest and most successful pre-Civil War campaign against Plains Indians, commanded troops charged with upholding federal authority in Kansas and Utah, and almost provoked hostilities with Great Britain in the Pacific Northwest. Removed from command amid false charges of disloyalty during the Missouri secession crisis, he returned as a leading member of the Indian Peace Commission of 1867-68. Harney was bold, ambitious, and innovative, but also impulsive, vindictive, and violent. His career illustrates the nineteenth-century army's role in implementing federal policy, highlights its limited resources compared to its responsibilities, and illuminates key aspects of its organizational structure, the behavior of its officers, and its impact on personal lives.