D - They proved their worth on the battlefield many times and earned the respect of the White Soldiers Union
Explanation:
Prior to the promulgation of the Executive Order 9981 by President Truman of the United States of America, segregation was very prominent in the United States armed forces. The black soldiers were separated from their white counterparts, and the white soldiers enjoyed varied benefits and privileges which were not available to the black soldiers. For instance, while it took the black soldiers 4 years before they can join the U.S combat after qualification , it only took the white soldiers few months. However, the colored unit of the U.S military made immense contributions to the success of the U.S military especially through their heroic exploits in the battlefield. This earned them respect before the White Soldiers Union, and was part of the facts that triggered the then U.S President Truman to pass the Executive Order 9981 which abolished segregation in the United States Armed Forces. This order was passed during the subsistence of the Korean War.
It was mostly "amassing the largest armies ever in one place" that resulted in the single bloodiest day in American history at the Battle of Antietam, since although this was technically a Union victory, both sides were fairly evenly matched.
