Beautiful, vivacious and fearless, Agnes Leclerc was 21 years old when she met Prince Felix Salm, a Prussian officer in the Union Army at the outbreak of the US Civil War. Their marriage took Agnes from small-town America to the royal palaces of Europe. She accompanied Felix on his Civil War campaigns, followed him to Mexico to fight for Emperor Maximilian, then returned home to his ancestral castle in Germany and war with France. Presidents, governors...