Final answer:
Black men commanded all-black units for the first time during the Civil War, notably after the Emancipation Proclamation in 1863, with regiments like the Massachusetts 54th Volunteer Infantry proving crucial in battle.
Step-by-step explanation:
Black men commanded all-black units for the first time in American history during the Civil War. The Emancipation Proclamation in 1863 opened the way for the widespread enlistment of black men into the Union Army and Navy, leading to the formation of regiments such as the Massachusetts 54th Volunteer Infantry. These regiments, often under the initial leadership of white officers, saw significant combat, proving their valor and laying claims to citizenship. Despite initial reluctance, black officers began to command these regiments, marking a pivotal moment in U.S. military history.
By the time of World War I, although African American soldiers served with distinction in labor and combat units like the Harlem Hellfighters, they were segregated and usually commanded by white officers. It was not until after World War II that the U.S. military branches began to integrate, furthering the leadership opportunities for African Americans within the military.