Final answer:
During the Civil War, black men in the U.S. Colored Troops composed ten percent of the Union army, serving in segregated units and contributing significantly to the war effort while also fighting for their rights and citizenship.
Step-by-step explanation:
Black men in the U.S. Colored Troops (USCT) composed ten percent of the Union army during the Civil War. The USCT were segregated units, serving in a range of military roles including infantry, cavalry, artillery, and engineering. Despite facing racism and unequal treatment, these soldiers proved their valor in over 400 battles, with fifteen receiving the Medal of Honor. The contribution of African American soldiers was significant, not only to the war effort but also in laying their claims to citizenship, challenging societal norms, and symbolizing the rejection of slavery.