 Complete the following phrase:  During the early stages of the civil war, Mayer took sides with abolitionism, and wrote several articles in Harpers 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 lieutet 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 