The history of African Americans in the American Civil War is marked by 186,097 (7,122 officers, 178,975 enlisted/soldiers & sailors) African Americans comprising 163 units who served in the United States Army, then nicknamed the "Union Army" during the Civil War. Later in the War many regiments were recruited and organized as the "United States Colored Troops", which reinforced the Northern side substantially in the last two years.
Many more African Americans served in the United States Navy also known as the "Union Navy" and formed a large percentage of many ships' crews. Both free African Americans and runaway slaves joined the fight.
On the Confederate/Southern side, both free and slave Blacks were used for manual labor, but the issue of whether to arm them, and under what terms, became a major source of debate within the Confederate Congress, the President's Cabinet, and C.S. War Department staff. They were authorized in the last month of the War in March 1865, to recruit, train and arm slaves, but no significant numbers were ever raised or recruited.
Our Presidents, Governors, Generals and Secretaries are calling, with almost frantic vehemence, for men.-"Men! men! send us men!" they scream, or the cause of the Union is gone...and yet these very officers, representing the people and the Government, steadily, and persistently refuse to receive the very class of men which have a deeper interest in the defeat and humiliation of the rebels than all others.
The issue of raising African American regiments in the Union's war efforts was at first met with trepidation by officials within the Union command structure, President Abraham Lincoln included. Concerns over the response of the border states (of which one, Maryland, surrounded the National Capital of Washington D.C.), the response of white soldiers and officers, as well as the effectiveness of a colored fighting force were raised.