The Great Depression lasted until the start of World War II. When the nation geared up for war with Germany and Japan, American workers went back to the factories and worked overtime to create the machinery of war. The nation united to fight common enemies, and African American leaders like DuBois urged black Americans to support the nation's war effort. In September 1940, more than a year before the United States entered World War II, the NAACP announced that black Americans would back their nation if it entered the European conflict: "Though thirteen million Negroes have more often than not been denied democracy, they are American citizens and will as in every war give unqualified support to the protection of their country."

Thousands of African American soldiers, sailors, airmen, and nurses took part in World...