"What did we go to war for, if not to protect our property?" - CSA senator from Virgina, Robert Hunter, 1865
What was the reason that induced Georgia to take the step of secession? This reason may be summed up in one single proposition. It was a conviction, a deep conviction on the part of Georgia, that a separation from the North-was the only thing that could prevent the abolition of her slavery. -- Speech of Henry Benning to the Virginia Convention
History affords no example of a people who changed their government for more just or substantial reasons. Louisiana looks to the formation of a Southern confederacy to preserve the blessings of African slavery, and of the free institutions of the founders of the Federal Union, bequeathed to their posterity. -- Address of George Williamson, Commissioner from Louisiana to the Texas Secession Convention
In the momentous step which our State has taken of dissolving its connection with the government of which we so long formed a part, it is but just that we should declare the prominent reasons which have induced our course.
Our position is thoroughly identified with the institution of slavery, the greatest material interest of the world. --Mississppi Declaration of the Causes of Secession
"[Recruiting slaves into the army] is abolition doctrine ... the very doctrine which the war was commenced to put down." - Editorial, Jan 1865, North Carolina Standard
The issue of Slavery may have motivated them to secession, but Lincoln informs us that it wasn't sufficient reason to induce them to stop fighting, in spite of his best efforts to concede the issue.
What I read, is that they fought a WAR because someone invaded them with an army.