In the Navy everybody onboard a ship in uniform is considered a "sailor" no matter what function he is titled, his job is needed to make the weapon, the ship, perform effectively. If any one fails his duty, the consequences could mean the loss of all onboard. There are no rear echelon troops onboard a warship.
An army in the field is basically the same if you look at it as a body of men who compose a weapon. Although an army's possible destruction is not so clear and final as a ship at sea, the premise is the same, every man must worked and perform his duty to make the army function effectively. If men within a certain army were sworn, paid, uniformed, came under military law and organized under military supervision, they were soldiers no matter what their function. If they were ONLY contractors, civil servants or camp followers/body servants (paid or unpaid) they were NOT soldiers.
The Confederates left a puzzle for us, because they did not keep a documented record of blacks within their armies that is readily and easily determined. However, we, (researchers I have worked with and or seen their work) keep finding evidence that the Union officials believed and reported there were Black Confederates and identified them under various descriptions which here are some examples:
"armed negroes", "negro skirmishers", "corps of Blacks", "black soldiers", "uniformed negroes", "colored rebel scout", "armed picked negroes", "negro prisoners of war", "negroes and mulattos organized under arms" and "Indians and half breed negroes and Indians organized in arms" ---These reports in the majority stated these men were integrated within Confederate armies in the field but rarely described them as Black organized field units, if at all.
So, for those who disagree there were Black Confederate soldiers, I empathize with that thought, but I cannot discribe these men referenced above as anything but Black Confederate soldiers or Confederate soldiers of color until I know exactly who they were and why they did not peacefully submit to the Union forces.