You want to know truth, here's a mouthful for you to choke on ... 'Lincoln through his secretary of state, called out the militia of twenty-four states using as authority a 1795 act of Congress that gave the president the authority to do so, providing that authority would cease thirty days after the beginning of the next session of Congress.
Under the Constitution it is the duty of the president to call the Congress into session during "extrordinary occasions." Ft. Sumter, like Pearl Harbor, was such an occasion. Why didn't Lincoln follow the commands of the Constitution and call the Congress forthwith? Why did he, on 15 April 1861, call Congress to meet almost three months later in July? And then only after he had driven the nation headlong into war? Obviously, he did not want Congress to get involved-did not want the Constitution to get involved. Lincoln was assuming all the powers of a dictator.
After calling forth the militia, within less than a week after Sumter, Lincoln ordered the blockade of Southern ports. A blockade is an act of war, requiring Congressional resolution. On April 21, he ordered the navy to buy five warships, an appropriations act requiring Congressional approval. On April 27th, he started suspending the priviledge of habeas corpus, in effect just about nullifying every civil liberty of every citizen. Soon thereafter he started shutting down newspapers that were not supportive of the war on the South. On May 3, he called for more troops, this time for three years, again a prerogative of the Congress.' - 'When In The Course of Human Events' - Charles Adams 1999
Yet you say that the South had no right to lawfully seceed. Please read what the Founding Fathers thought about rebellion!
It is a traditional American motto that: "Rebellion to tyrants is obedience to God." That is, resistance against tyranny is a moral duty. This motto was suggested by Benjamin Franklin in mid-1776 in the Congress as being an appropriate one for the seal of the United States; and it was so truly expressive of traditional American thinking that Jefferson adopted it for use on his personal seal.
A major part of the American philosophy underlying the resistance to the tyranny of the king and parliament prior to the Declaration of Independence, and in support of that Declaration in 1776, was as follows. Public officials who exceed the limits of the powers delegated to them by the people under their fundamental law and thus violate, or endanger, the people's God-given, unalienable rights thereby and to this extent make of themselves defaulting trustees, usurpers, oppressors and tyrants. They thereby act outside of this supreme law, which defines these limits and the scope of their authority and office, and therefore act without authority from the people. By thus exceeding and violating the restrictions of law, they act outside the Law: lawlessly, as "out-laws." As Samuel Adams stated: "Let us remember, that 'if we suffer tamely a lawless attack upon our liberty, we encourage it, and involve others [Posterity] in our doom.'" (Emphasis added.) They thereby, in practice, replace Rule-by-Law with Rule-by-Man. These defaulting trustees-thus acting lawlessly-thereby free the people from any duty of obedience; because legally and morally, under Rule-by-Law, obedience by the self-governing people is required only to Law and not to law-defying public servants.
The reasoning supporting the above-quoted motto's concept of moral duty is this: Man, being given by his Creator unalienable rights which are accompanied by corresponding duties, has the moral duty - duty to God - to safeguard these rights for the benefit of self and others, including Posterity. Man is therefore obligated to oppose all violaters of these rights and to fail to do so is to defy duty to God as the giver of these rights; and such failure betrays Man's duty as the temporary trustee of Posterity's just heritage.- 'The Spirit of 1776 - Twelve Basic American Principles' by Hamilton Albert Long published 1976 (Emphasis is mine)
So as we see, the South had every right to secede and not obey the tyranny of Lincoln who had usurped his Constitutionally delegated powers.