I tend to believe that race relations played a relatively minor role during the American Civil War. Although one of the primary reasons the Southern states seceded was because they were losing power in Congress (due to more newer states being declared "free states"), the Confederacy went to war primarily to defend their independent status--not to protect their right to own slaves. As mentioned in a previous post, Lincoln did not believe in the equality of black and white men; his Emancipation Proclamation was intended to give the slaves in the South a reason to remain hopeful for their own freedom and to undermine the Confederacy's status as one of the few remaining slave-owning nations in the world. Many Southern slaves remained faithful to their owners throughout the war, and some slaves even fought alongside their masters in the Confederate armies. Perhaps the most important way that Negroes affected the war was in the large numbers of black troops that were mustered into the Union armies during the last years. It gave the Federal armies another resource from which to draw--one which the Confederacy refused to consider.
This is an interesting question. On one hand, the fight over slavery, the enslavement of Black people, would be on face value, holding importance regarding the conflict. Yet, once the conflict began, the issue of race seemed to disappear. I agree with the previous thoughts echoed on this point. I think that each side might have entered the conflict with some premise of race on their plates, but once it commenced, the priorities shifted away from race. Again, it seems odd because the abolitionist voices in the North and the anti- abolitionist voices in the South were very loud and filled with rancor. Yet, each side became relegated to the sidelines once the conflict started. The South was not really driven by slavery as much as seeing victory against the North as something that would silence them once and for all. The South also saw the war as a way to demonstrate their own superiority and confidence in their own way of life. Slavery was a part of this, but it was broached in the larger sense to include "tradition" and the "right to be left alone." These are more Constitutional in nature and not driven by race. The North was animated by the preservation of the Union. Once the war started, there was little in way of motivation to equalize out racial conditions or speak for a voice that had been silenced for centuries. Race seems to have played a prominent role on the outset, but then became a silent one throughout. Perhaps, this speaks quite lucidly to the condition of race in America as one in silence, and not being able to experience full articulation.
Race and the anti-slavery movement did play a role in the war. After the Battle of Antietam in September of 1862, Lincoln issued the Emancipation Proclamation. He did this for a number of reasons. First, it turned the war into a war to end slavery, not just to save the Union. This gave added incentive for some northerners to fight and to get African Americans to join the fight against the Confederacy. It also helped keep Great Britain out of the war. Britain abolished slavery decades before and would not join the side that was defending slavery. So in this respect, race did play somewhat of a role in the Civil War.
In my opinion, race played very little role in causing the American Civil War. Slavery did play a role in causing the war, but the North was not fighting to free the slaves and they were certainly not fighting because they believed in racial equality.
One piece of evidence for this is the fact that Abraham Lincoln himself did not believe in racial equality. He is quoted as saying that blacks were naturally inferior to whites and that they could never really live together in the same country. He was one of the main driving forces behind the war and he was not in any way interested in the idea of racial equality.
In general, the North was fighting to keep the Union together. Sure, some Northerners were abolitionists and some (very few) believed in racial equality. But that is not what the war was about.