“You will find me very much changed in everything but outside appearance when I come home,” Corporal Thomas H. Mann (1843–1916) warned his parents toward the end of the Civil War. A native of North Wrentham (now Norfolk), Massachusetts, Mann was a member of Company I of the Eighteenth Massachusetts regiment—part of the heralded Army of the Potomac—and saw action in many of the most pivotal and bloody battles of the war, including Second Manassas, Antietam, Fredericksburg, Chancellorsville, Gettysburg, and the Wilderness. In his memoir, written in the late nineteenth century and discovered by his grandsons among family papers a century later, Mann offers a riveting account of his battlefield experiences and paints a vivid portrait of a young man coming of age through a gauntlet of horror and suffering. Mann was highly literate, well read, perceptive, and witty—he was headed for Harvard before the war altered his course—and his memoir is an unusually eloquent account of the impact of war in all its forms. Drawing heavily on his wartime letters and on the recollections of his comrades, Mann colorfully reconstructs his wartime travels and trials from his enlistment to his capture at the Wilderness—the nightmare of the battlefield, the particulars of camp life, southern civilians struggling amidst shortage and destruction, freed slaves flocking to the army by the hundreds. With a keen editorial eye, John J. Hennessy delicately blends Mann’s various writings into a cohesive, captivating narrative. Possessing an acute political and social awareness, Mann reveals himself to be the classic example of a conservative patriot. He rails against many of his government’s policies—including emancipation, confiscation, and war on civilians—but he loves his country and fights desperately to preserve it. He enters the war vigorous, enthusiastic, wide-eyed, and determined and leaves it skeptical and broken down. Nonetheless, he is proud of his participation. Mixing postwar memory and reflection with the immediacy of wartime letters, Fighting with the Eighteenth Massachusetts is a historiographical rarity: memoir interwoven closely with, and supported by, wartime documents. The result is a poignant chronicle of a remarkable young man during America’s most troubled time.