An excerpt: In 1855, John Singleton Mosby, newly graduated from the University of Virginia, had opened a law office at Bristol, Washington County, Virginia, and a year later he had married. The son of a well-to-do farmer and slave-owner, his boyhood had been devoted to outdoor sports, especially hunting, and he was accounted an expert horseman and a dead shot, even in a society in which skill with guns and horses was taken for granted. Otherwise,...