From 1862 to 1865, Moseley fought in the Civil War as an infantry soldier in Wisconsin's 22nd Volunteers. Briefly captured and interred in a Confederate POW Camp, he returned to action and participated in Sherman's Atlanta campaign. He marched in the Washington, D.C., Grand Review before returning to the Beloit area, where he remained for the rest of his life.

Mosely wrote detailed missives to his family in Beloit about his wartime experiences, demonstrating a flair for describing both camp life and battles. Frank and forthright, he was remarkably articulate, insightful, and thoughtful, whether describing mundane activities or the nearly unfathomable death of President Lincoln. These 125 letters, never before made available to scholars or students of the war, became touchstones and sources of pride for the Moseley family-and provide a uniquely candid and vivid view of this tumultuous period in US history.