The Abraham Lincoln Brigade was a group of American volunteers who fought in the Spanish Civil War in 1936-1938. The brigade, part of the larger International Brigades volunteer corps, comprised of 2800 Americans fighting for the Spanish Republicans against General Franco's Nationalist forces.
The corps integrated black and white soldiers and promoted a black commander, Oliver Law, in 1937 (read more about Law here).
Many Americans saw this as an opportunity to fight fascism. Volunteers were recruited by the U.S. Communist party, which aided the Spanish Republicans in their fight against Franco's uprising.