All-black soldiers from the Ninth and Tenth regiments of the US cavalry, is the right answer.
The members of the Tenth Cavalry Regiment of the U.S. which was formed on 21st September 1866 at Fort Leavenworth, Kansas, were known as the Buffalo Soldiers. This was a name assigned to the Black Cavalry by the local tribes of the United States played a significant role in the Indian Wars. However, during the course of time, this term became synonymous with all the regiments of the African-Americans formed in the year 1866 such as the Ninth and Tenth Cavalry Regiment and Twenty-fourth and Twenty-fifth Infantry Regiment.
