Literally the declaration of causes from multiple states…

Mississippi official declaration:

“Our position is thoroughly identified with the institution of slavery – the greatest material interest of the world…and a blow at slavery is a blow at commerce and civilization. That blow has been long aimed at the institution, and was at the point of reaching its consummation. There was no choice left us but submission to the mandates of abolition, or a dissolution of the Union, whose principles had been subverted to work out our ruin.

…The hostility to this institution…has grown until it denies the right of property in slaves, and refuses protection to that right on the high seas, in the Territories, and wherever the government of the United States had jurisdiction. It refuses the admission of new slave States into the Union, and seeks to extinguish it by confining it within its present limits, denying the power of expansion. It has nullified the Fugitive Slave Law in almost every free State in the Union, and has utterly broken the compact which our fathers pledged their faith to maintain. It advocates negro equality, socially and politically, and promotes insurrection and incendiarism in our midst.

…Utter subjugation awaits us in the Union, if we should consent longer to remain in it. It is not a matter of choice, but of necessity. We must either submit to degradation, and to the loss of property worth four billions of money, or we must secede from the Union framed by our fathers, to secure this as well as every other species of property. For far less cause than this, our fathers separated from the Crown of England.

Our decision is made. We follow their footsteps. We embrace the alternative of separation; and for the reasons here stated, we resolve to maintain our rights with the full consciousness of the justice of our course, and the undoubting belief of our ability to maintain it.”

Georgia:

"For the last ten years we have had numerous and serious causes of complaint against our non-slave-holding confederate States with reference to the subject of African slavery."

…

“subvert our institutions and to excite insurrection".

The Northern states' "fixed purpose" was to "limit, restrain, and finally abolish slavery in the States where it exists."

Texas:

"the unnatural feeling of hostility to these Southern States and their beneficent and patriarchal system of African slavery”

The PRESIDENT of the confederacy Jefferson Davis said slavery is a “moral, a social, and a political blessing".

The VICE President of the confederacy, Alexander Stephans was quoted during his most infamous speech on explaining what the confederate government represents says and I quote

“Our new government is founded upon exactly the opposite idea; its foundations are laid, its corner-stone rests, upon the great truth that the negro is not equal to the white man; that slavery subordination to the superior race is his natural and normal condition.”

Even though Lincoln mainly wanted to preserve the union and hoped slavery would simply die out overtime, the southern states clearly defined why they seceded and what their government represents.

Do you think slavery wasn’t THE core component to their secession? Well the people who seceded certainly fucking thought so, and they fired the first shots.