What Happened to Free Black Americans (in Northern/border states) who found themselves under Confederate occupation during Confederate offensives in the American Civil War? Were they sold into slavery?

by GauntBilly

I can't find any real good sources about what happened to free black Americans who came under Confederate occupation. I saw a post that said they were deported and sold into slavery during Gettysburg and Bull Run, but couldn't find anything that backed up those claims. Generally when I searched that, I only found what happened to slaves who came under Union control.

Georgy_K_Zhukov

There was only one major Confederate offensive into a free state, which was the Gettysburg campaign. This older answer of mine goes into more depth on this.