Short answers, pulled from the story.
The United States War Department issued General Order Number 143 on the 22nd of May 1863, establishing the Bureau of Colored Troops to facilitate the recruitment of African-American soldiers to fight for the Union Army.
Approximately 175 regiments comprising more than 178,000 free blacks and freedmen served during the last two years of the war. The total number of colored troops from the North was 79,283, while those from the South numbered 93,796.
The first engagement by African-American soldiers against Confederate forces during the Civil War occurred at the Battle of Island Mound in Bates County, Missouri on the 28th of October 1862. African Americans mostly escaped slaves had been recruited into the 1st Kansas Colored Volunteers to break up Confederate guerrilla activities based out of Hog Island near Butler, Missouri.
The Congress of the Confederate States of America passed a law on the 1st of May 1863 stating that white officers commanding black soldiers and blacks captured in uniform would be tried as rebellious slave insurrectionists in civil courts with an automatic sentence of death. In practice USCT soldiers were often murdered by Confederate troops without being taken to court because the Confederacy announced that former slaves fighting for the Union were traitors.
Sergeant William Harvey Carney of the 54th Massachusetts (Colored) Volunteer Infantry received his medal 37 years after the battle where he saved the flag at Fort Wagner in July 1863. He earned the nation's highest award for service in the war despite being wounded multiple times while carrying the colors back to Union lines.