The southron myth machine at work yet again. Yes, there was a rebellion. Yes there was an insurrection. Whatever the hell 'c' means. You don't invade your own country so nobody invaded anyone.
There was no insurrection. The South never attempted to conquor the central government, only to peacefully leave it. Davis would not even allow Stonewall to attack Washington following Manassas I, because, "all we wish is to be left alone."
As for slavery:
On March 2, 1861, the U.S. Senate passed a proposed Thirteenth Amendment to the US Constitution (which passed the House of Representatives on February 28) that would have prohibited the federal government from ever interfering with slavery in the Southern states. (See U.S. House of Representatives, 106th Congress, 2nd Session, The Constitution of the United States of America: Unratified Amendments, Document No. 106-214, presented by Congressman Henry Hyde (Washington, D.C. U.S. Government Printing Office, January 31, 2000). The proposed amendment read as follows:
No amendment shall be made to the Constitution which will authorize or give to Congress the power to abolish or interfere, within any State, with the domestic institutions thereof, including that of persons held to labor or service by the laws of said State.
Two days later, in his First Inaugural Address, Abraham Lincoln promised to support the amendment even though he believed that the Constitution already prohibited the federal government from interfering with Southern slavery. As he stated:
I understand a proposed amendment to the Constitution . . . has passed Congress, to the effect that the Federal Government shall never interfere with the domestic institutions of the States, including that of persons held to service. To avoid misconstruction of what I have said, I depart from my purpose, not to speak of particular amendments, so far as to say that, holding such a provision to now be implied constitutional law, I have no objection to its being made express and irrevocable.
This of course was consistent with one of the opening statements of the First Inaugural, where Lincoln quoted himself as saying: "I have no purpose, directly or indirectly, to interfere with the institution of slavery in the States where it exists. I believe I have no lawful right to do so, and I have no inclination to do so."
Thats what Lincoln said his invasion of the Southern states was not about. In an August 22, 1862, letter to New York Tribune editor Horace Greeley he explained to the world what the war was about:
My paramount object in this struggle is to save the Union, and it is not either to save or destroy slavery. If I could save the Union without freeing any slave, I would do it; and if I could save it by freeing some and leaving others alone I would also do that. What I do about slavery, and the colored race, I do because I believe it helps to save the Union.
Of course, many Americans at the time, North and South, believed that a military invasion of the Southern states would destroy the union by destroying its voluntary nature. To Lincoln, "saving the Union" meant
destroying the secession movement and with it the Jeffersonian political tradition of states rights as a check on the tyrannical proclivities of the central government. His war might have "saved" the union geographically, but it destroyed it philosophically as the country became a consolidated empire as opposed to a constitutional republic of sovereign states.
On July 22, 1861, the US Congress issued a "Joint Resolution on the War" that echoed Lincolns reasons for the invasion of the Southern states:
Resolved: . . . That this war is not being prosecuted upon our part in any spirit of oppression, nor for any purpose of conquest or subjugation, nor purpose of overthrowing or interfering with the rights or established institutions of those states, but to defend and maintain the supremacy of the Constitution and all laws made in pursuance thereof and to preserve the Union, with all the dignity, equality and rights of the several states unimpaired; and that as soon as these objects are accomplished the war ought
By "the established institutions of those states" the Congress was referring to slavery. As with Lincoln, destroying the secession movement took precedence over doing anything about slavery.