Born in Athlone, Ireland in 1827, James Fegan served some time with the Irish Constabulary prior to emigrating to the United States in 1850. After arriving in New York City, New York, he enlisted as a private in the U.S. Army and assigned to Company I of the 2nd U.S. Infantry on October 29, 1851. By the end of his first enlistment in 1856, he had risen to the rank of sergeant. Fegan remained with his unit up to and during the American Civil War. As part of the Army of the Potomac, he saw action at Gaines' Mill, Malvern Hill, Hanover Court House, Fair Oaks, Harrison's Landing, Bull Run, Centreville, South Mountain and Antietam. Though seriously wounded at Antietam, having taken a bullet in the right leg, he reenlisted in Company C of the 3rd U.S. Infantry on March 31, 1864. He held a distinguished war record, having been wounded several times in action, and participated in a number of major battles during the final years of the war. Among these included the battles of Petersburg, Reams' Station, James' Station, Birney Station, Stoneman's Creek, the first and second battles of Deep Bottom, South Side Railroad, Danville Railroad, Boydton Plank Road, Appomattox Station, Farmsville City, New House, Savage's Station, Reno Station, Manchester, Richmond, Dunwiddie, Burksville Junction, Appomattox Courthouse and the subsequent surrender of General Lee's Army.