Pyrrhic is defined as a victory that is won at too great a cost to have been worthwhile for the victor. In context, the North and the South each experienced major victories during the war. Victories, however, could not make up for the massive destruction and loss of life.
"I can't quite see how they're callin' it a vict'ry," he said, his eyes fixed on the ground as they walked along the furrow. "If we'd got down to Corinth and pushed the Rebs out, that would hev bin good news. This way, looks to me like all we done was to keep the Rebs from hevin' a vict'ry."
"What do you s'pose it was like, Jeth?"
He shook his head. "It must ha' seemed like the end of the world had come, " he said soberly.
"Fer thousands it had, hadn't it?"