United States Colored Troops (USCT) were Union Army regiments during the American Civil War that primarily comprised African Americans, with soldiers from other ethnic groups also serving in USCT units. Established in response to a demand for more units from Union Army commanders, USCT regiments, which numbered 175 in total by the end of the war in 1865, constituted about one-tenth of the manpower of the army, according to historian Kelly Mezurek, author of For Their Own Cause: The 27th United States Colored Troops. “They served in infantry, artillery, and cavalry.” Approximately 20 percent of USCT soldiers were killed in action or died of disease and other causes, a rate about 35 percent higher than that of white Union troops. Numerous USCT soldiers fought with distinction, with 16 receiving the Medal of Honor. The USCT regiments were precursors to the Buffalo Soldier units which fought in the American Indian Wars.

During the American Civil War, the United States Army, the land force that fought to preserve the collective Union of the states, was often referred to as the Union Army, the Grand Army of the Republic, the Federal Army, or the Northern Army. It proved essential to the restoration and preservation of the United States as a working, viable republic.