Certainly, you could make a case that what motivated Southern troops was a combination of slavery, states rights or allegiance to a Southern identity, but when it comes down to it — the leadership of the South seceded to protect the “peculiar institution”.

For the North, it was a more complex case for motivating the troops — it was a fight to set men free, yes; but Northerners were not uniformly looking to aid Southern blacks. Many were motivated by the need to preserve the Union more than abolition, conscripted Irish and other immigrants were certainly not thrilled with the idea of coming to America to escape English mistreatment, only to be throw in blue and used as meat shields for Northern politicians and activists who wanted to end slavery and preserve the Union…and maybe break the hold of Southern senators on getting Western land for Northern railroad concerns, along with a few other big economic issues.