Thousands of African Americans willingly participated in the military actions in the Civil War, and many more offered support behind the lines. Southern blacks who volunteered for the Confederate Army were assigned to heavy labor, not battle. As the war turned against the South, more and more blacks fled to the Union forces.

In the North, noted speakers such as Frederick Douglass urged free blacks to fight for the Union, and worked to convince the government to use them. In spite of the army's reluctance, the Union Navy made extensive use of black sailors. By 1862, the courage and ability in battle displayed by African American soldiers changed the government's policy, and it began to enlist soldiers into segregated, all-black units. At least 180,000 black men enlisted in the Union Army, 30,000 in the navy.