I have many books about the war and there are a couple of books made back in the 50’s and 60’s.
In them are letters from soldiers on both sides and there is hardly a mention about slaves or slavery.
Another point.
When you look at the books made back in the 50’s and 60’s to today then there is a massive difference on the facts.
Grant and a whole host of Union generals said that if the War was to free the slaves they would not have supported it. They were adamant that they fought to preserve the Union, as they saw it (a noble cause if the Union — and the federal government that ran it — was going to abide by the Constitution, which it didn’t).