After they killed 300,000 Yankee soldiers.
And as I mentioned before, with less resources.
And the south lost almost 270,000 during the rebellion. And then quit. So talk about 'dead having died in vain'.
Union KIAs were about 110,000 while about 200,000 died from from non-combat causes, mostly disease of some sort, which was the sad lot of soldiers in the 19th century.
No one knows with any accuracy how many rebels died in combat since the Confederates didn't keep very good records. Most estimates say somewhere between 90,000 and 100,000 KIAs. The numbers of those lost to non-combat causes is even less well understood.