During the early stages of the civil war , Mayer took sides with abolitionism , and wrote several articles in Harper 's Magazine , stressing the role of African slaves ' descendants in the South American Independence wars . He helped to establish a number of colored regiments . He joined the Union Army in July 1863 as a captain . Promoted to the rank of lieutenant colonel , he fought with distinction in Chattanooga , Olustee and the Siege of Petersburg , commanding the 45th U.S. Colored Infantry Regiment . At the time of Lincoln 's assassination , Mayer and his men were at a party along with his friend Robert Lincoln . Mayer attended Abraham Lincoln 's funeral , comforting his friend and family
Lincoln 's assassination
Assassination of Abraham Lincoln
Edelmiro Mayer