"Relatively few people are aware that during the Civil War, Confederate leaders put forth a proposal to arm slaves to fight against the Union in exchange for their freedom."
They are probably also unaware that the Union Army exempted blacks from the draft at first and massive riots broke out targeting blacks in the North.
Before the war was over, both blacks and whites were being forced to either become soldiers or civilians war workers, the blacks at reduced pay.
Was it at Fredricksburg where the Union troops refused to fight with their black compatriots?