My reading of McPherson suggested Lee's victories during the Seven Days Battles led to Lincoln's resolve to free the slaves. Up until that point, the North was

My reading of McPherson suggested Lee's victories during the Seven Days Battles led to Lincoln's resolve to free the slaves. Up until that point, the North was hoping to quickly force the South into submission with their institutions largely intact. But Lee's unexpected success raised the stakes into an all-or-nothing ragnarok in which the South, along with slavery, had to be annihilated.