Seven days before Lee’s surrender, Lieutenant Otho McManus was killed leading a battle charge in Alabama. During the previous thirty months, the young Midwestern schoolteacher wrote more than a hundred letters. His polished writing reflects his hopes, ambitions, fears, war experience and domestic concerns. The letters describe his capture while rescuing a wounded cousin, a deadly case of friendly fire, opinions of officers and war prospects, and strong feelings about anti-war dissent. McManus served in the 123rd Illinois Mounted Infantry. This regiment was an integral component of the elite Wilder’s Lightning Brigade. Wilder’s Brigade played pivotal roles in battles and campaigns in Tennessee, Georgia and Alabama. McManus’ letters include extended accounts of the battles of Chickamauga, Hoover’s Gap and Perryville and the Atlanta Campaign, among other campaigns, battles and skirmishes. The editors have supplemented the letters with a detailed chronology of the regiment’s movements, with an account of explosive political developments in McManus’ home country, and with post-war sketches of people mentioned in the letters. The editors have also included statistical analyses of the regiment’s demographics, mortality and desertion rates. The commentary is based on hundreds of commanders’ reports from the Official Records of the War of the Rebellion, from dozens of pension and compiles service records, from more than a dozen court-martial transcripts, and from other soldiers’ diaries and letters.