secede
A verb
1 secede, splinter, break away
withdraw from an organization or communion; “After the break up of the Soviet Union, many republics broke away”
secession
A noun
1 secession, withdrawal
formal separation from an alliance or federation
I'll defer to Mr. Davis:
“First, he said, came that spurious and decayed off-shoot of democracy, which, claiming that this Federal government has no power, leaves the people our next greatest evil, despotism; and denies protection to our Constitutional rights. Next comes the party that proclaims the Union and the Constitution, but that dares not tell what the Constitution is—a mere catchword, sounding, but meaning nothing. Then, my friends, there is the “rail-splitter,” aptly selected for the purpose, first proclaiming there was an “irrepressible conflict” between the sections; and having proved himself able to rend the yoke, who so fit as he, with such a theory as that, to be selected for the accursed performance of rending the Union? Then, my friends, comes the true democracy, proclaiming the Constitution and the Union, and what the Constitution is; writing your opinions on your banner, throwing it to the winds, and inviting all who believe to command worship at the altar of truth. [Applause.] This banner proclaims the futility of Abe Lincoln's efforts to rend the Union. Though he did rend the yoke, he will find the Constitution and the Union worse than any black gum in the forest.
Our cause is onward. Our car is the Constitution; our fires are up; let all who would ride into the haven of a peaceful country come on board, and those who will not, I warn that the cow- catcher is down—let stragglers beware! [Cheers.] We have before us in this canvass the highest duty which can prompt the devoted patriot. Our country is in danger. Our Constitution is assailed by those who would escape from declaring their opinions—by those who seek to torture its meaning, and by those who would trample upon its obligations. What is our Union? A bond of fraternity, by the mutual agreement of sovereign States; it is to be preserved by good faith—by strictly adhering to the obligations which exist between its friendly and confederate States. Otherwise we should transmit to our children the very evil under which our fathers groaned—a government hostile to the rights of the people, not resting upon their consent, trampling upon their privileges, and calling for their resistance. But I place my trust in democracy—in that democracy which has borne this country on from its commencement, which has illustrated all its bright passages of history, which has contributed to it all which is grand and manly, all which has elevated and contributed to its progress—the democracy of Washington, of Jefferson, of Jackson, and of Buchanan [great applause] shall be the democracy of the next four years. [Renewed applause.]”
The national democracy present a ticket to the country which may well inspire the most lofty patriotism. The name of Breckinridge comes down by lineal descent from one who asserted the great principles of 1798, as reaffirmed at Baltimore; and as for Lane, he is too modest to boast of the deeds of his younger days. No doubt he has split a hundred rails to Lincoln's one! [Laughter and cheers.] Let us then be encouraged to go into the conflict, determined to succeed, and transmit to our children the rich inheritance we have received from our fathers unimpaired. [Applause.] "
Rebellion
Noun
Open, armed, and usually unsuccessful defiance of or resisance to an established government.
I'll defer to Mr. Davis:
I'll defer to Chief Justice Chase:
"When, therefore, Texas became one of the United States, she entered into an indissoluble relation. All the obligations of perpetual union, and all the guaranties of republican government in the Union, attached at once to the State. The act which consummated her admission into the Union was something more than a compact; it was the incorporation of a new member into the political body. And it was final. The union between Texas and the other States was as complete, as perpetual, and as indissoluble as the union between the original States. There was no place for reconsideration or revocation, except through revolution or through consent of the States.
Considered therefore as transactions under the Constitution, the ordinance of secession, adopted by the convention and ratified by a majority of the citizens of Texas, and all the acts of her legislature intended to give effect to that ordinance, were absolutely null. They were utterly without operation in law. The obligations of the State, as a member of the Union, and of every citizen of the State, as a citizen of the United States, remained perfect and unimpaired. It certainly follows that the State did not cease to be a State, nor her citizens to be citizens of the Union. If this were otherwise, the State must have become foreign, and her citizens foreigners. The war must have ceased to be a war for the suppression of rebellion, and must have become a war for conquest and subjugation."