The Battle of Monocacy, which took place on the blisteringly hot day of July 9, 1864, is one of the Civil War's most significant yet little-known battles. What played out that day in the corn and wheat fields four miles south of Frederick, Maryland., was a full-field engagement between some 12,000 battle-hardened Confederate troops led by the controversial Jubal Anderson Early, and some 5,800 Union troops, many of them untested in battle, under the...