While black men had fought in various colonial wars and the American Revolution, the creation of the United States Colored Troops during the Civil War was something new. While black soldiers had previously numbered in the hundreds or thousands, nearly 180,000 men joined the USCT.

The biggest practical impact the USCT had was allowing the Union to easily garrison large segments of the South. Black soldiers were understandably treated like heroes by newly freed people, and were unlikely to pillage former slaves. This made them ideal for securing majority-black sections of the Deep South, both during the war and in the long years of Reconstruction. Many former USCT soldiers settled in the South after leaving the service. These men formed the spine of federal support in the former Confederacy, forming Union Leagues to build the Republican Party effectively from scratch and joining militias to fight the Klan and other Confederate dead-enders.

Black troops did not uniformly fight better than white troops. Some black regiments achieved glory and success, others did poorly. USCT units operated under some special conditions, however. The first is that all of their officers were volunteers. The Army, quite wisely, realized that assigning white officers at random to a black regiment could lead to disaster. As such, they called for volunteers, attracting an officer corps that, on the main, truly believed in abolition and were not virulent, outright racists. Secondly, black soldiers knew they would either be executed or enslaved if they were captured, since the Confederacy viewed the employment of black soldiers against white troops as a war crime. Knowing surrender was not an option, black regiments tended to be tenacious fighters.

Socially, the impact of the USCT was massive. The racist ideology slavery hinged on held that black people, and particularly black men, were stupid, brutish, and ultimately cowardly. Black soldiers outfighting the army of slave owners put the lie to this myth for all to see. As Confederate politician Howell Cobb said (in reference to a Confederate plan to enlist black soldiers), "If slaves make good soldiers our whole theory of slavery is wrong."

Black service in the Civil War also gave African-Americans an uncontestable claim to belonging in the United States; who could tell men who had fought and died for the Union to get back to Africa? The USCT helped committed the United States to a future as a multiracial society.

Sources:

William H. Freehling, The South vs The South

Steve Hahn, A Nation Under Our Feet

Eric Foner, Reconstruction