It is important to immediately note that there are two widely held misconceptions about the original nature of the American Civil War.
The misconception about the North is that they went to war for the purpose of ending slavery. While there were people in the north who wanted to end slavery, and while the main "cause" of the war was slavery, and while the war would eventually turn into a struggle to end slavery; the purpose of the war at its beginning was to settle the question of whether individual states could legally withdraw from the union unilaterally. What would otherwise be considered an issue of contract law. The idea being that each state had voluntarily surrendered certain powers to the federal government with the understanding that they were free at anytime to withdraw those powers. The counterargument being that once the states were melded together into one nation and operated that way for a number of decades, too much was interchanged, fused together, and conditioned on the status quo to make it feasible to return things to what they had once been; that an explicit non-binding contract had become binding.
The "generally" held northern position on slavery was that it should not be permitted in the territories and that no new slave states should be created.
The misconception about the South is that they were the revolutionaries. When James Mason and John Slidell went to Europe as Jefferson Davis's commissioners to the governments of England and France in late 1861, they were to make clear that the South was making no revolution. It was simply trying to get away from a revolution which aggressive Northern sectionalists had tried to make "in the spirit and ends of the organic law of their first union". A Second American Revolution had been brewing for some time up North and while there was no immediate threat to the institution of slavery where it already existed, the institution could be expected to come under increasing pressure over the next several decades as the free states continued to gain in relative power.
There was an extreme arrogance about the original secession, the most fatal result being the degree to which it caused them to miscalculate the dedication of those in the North to the preservation of the union. The concept of a unilateral secession reflected this arrogance. It was a Constitutional issue with no precedent, and a mutually agreed upon peaceful secession was a realistic and reasonable action. Indeed, since the two countries would share a long border a peaceful secession was prudent. Only someone so arrogant as to be dismissive would have believed otherwise. And there was considerable logic in an arrangement that provided for mutual defense and the sharing of certain services like mail, telegraph, and transportation.
But by its nature the unilateral secession was a hasty affair, a striking while the iron was hot and taking irrevocable steps while everyone's blood was up. The relative power of the extremist was peaking and they needed to act. Firing on Fort Sumter and Lincoln's call to raise an army allowed the extremists to prolong what would otherwise have been a very short period of control.
There were also two rarely discussed "common man" factors that drew the apathetic in both regions into the conflict. Southerners were simply tired of being condemned by Northerners for their hypocrisy, western tradition told them perpetual slavery was wrong and they struggled during the decade of the 1850's to rationalize the institution. But this rationalizing was made much easier but the constant badgering of the anti-slavery movement. On the other hand, many Northerners were indifferent to secession, and would have written it off as good riddance but for the timing. For decades they had accepted Southern elected dominance of the Federal government as the price of living in a democracy. Then within weeks of an election that ended this dominance the slave states refused to accept the outcome and bolted from the union. This was symbolically an assassination of the republic, little different than the assassination of an a lawfully elected official by someone only willing to participate in the democratic process if it resulted in the election of their candidate. A unilateral action to invalidate the election results to which they had implicitly agreed to be bound. Had secession occurred in 1858 or even in 1863 this reaction would have been on a much smaller scale.
The Confederate provisional constitution was notable for its exclusion of "We, the people" from the opening sentence. Catton felt this was done to "suppress the faint, haunting echo of Democracy's trumpets"; to make it clear that the people were acting through sovereign and independent states rather than just as people. This of course had an anti-egalitarian flavor, as did most of the other changes made to improve the machinery of government. Although preserving slavery was the biggest concern and motivation of the delegates assembled in Montgomery, there was the related belief that an aristocratic society would be able to govern itself better than a democracy. Undiluted democracy was indeed the main thing from which the cotton belt was seceding, distancing themselves from the: "unprincipled, cold-blooded, tyrannical, remorseless horde of Abolitionists, whose anti-slavery creed but thinly disguises mob-law and agrarianism which surely overtakes all free society and which is the root of all Republican offending". A monarchist, nativist, Know-Nothing reaction to the changes that had taken place in the country over the past two decades.
Interestingly the provisional constitution prohibited the old African slave trade, which the more dreamy-eyed visionaries of a growing slave-state empire had talked of reviving. Most likely this was for pragmatic reasons. Great Britain, a customer and potential ally, had aggressively clamped down on this activity with its navy. And the Caribbean and South & Central America had a ample supply of slaves for purchase or for eventual seizure once the new Confederacy got down to the business of territorial expansion.
The Montgomery convention (six states plus late arrival Texas) that brought the Confederate government into being was not the established South but the new cotton South, a group making immense profits out of slave-produced cotton. This was a frontier society in which the acquisition of land and slaves stood as the visible symbols of prosperity, a society that saw in the growth of abolitionism a direct threat to the boom times that enabled aggressive men to get rich. At the time they were not defending an old established aristocratic culture (insert "Gone With The Wind" here) from a stirring-up of racial antagonisms; that sentiment would later be enlisted on behalf of the cause but it was not central to the "originators" of secession.
In fairness to the South, the portrayal of antebellum southerners as a people united in a belief that the south was a wonderful place and the zenith of civilization is highly exaggerated. For many it was less an admiration for their institutions and culture than it was distaste and fear of what was developing culturally as the northeast became increasingly industrialized. Even someone like Alexander Stephens was in love with his idealized version of southern culture, perfectly aware that reality fell far short of his vision but believing that this vision was realistically attainable.
The Irony That Was McClellan: The hope that the war could be something less than a revolutionary struggle (the North being the revolutionists) died somewhere between Mechanicsville and Malvern Hill (The Seven Days - June 1862). Secession was an obvious miscalculation by the South and up until this point there was still a chance of bringing an early end to the struggle and ending the whole affair with only a modest amount of social change. It had become obvious to discerning Southerners by early 1862 and particularly after the fall of New Orleans that the war was lost. Settlement of the conflict was only a matter of pride at that point and victory by McClellan at Richmond in June (or ideally months before) would have convinced enough people that the cost of their pride was simply too high. It was not yet a war of emancipation and McClellan was terrified that it would soon move in that direction. The irony was that it was his timidity and vacillation that provided the time for things to escalate to the point where this is exactly what it became.
McClellan deserves considerable study because much of his negative influence has gone unexamined. He recognized that his actions could have a profound influence on the depth of the conflict but completely misread the implications. Sitting at Harrison's Landing at the effective end of the campaign he rationalized his failure to take aggressive action: "If I had succeeded in taking Richmond now the fanatics of the North might have been too powerful & reunion impossible". Then he switched gears and asked: "Does the President design to cause defeat here for the purpose of prolonging the war?" Poor McClellan was a psychological basket case, bedeviled by phantom confederate armies and the Lincoln Administration's failure to give him an even more overwhelming force with which to go on the offensive. Deluding himself about his own brilliance and excusing his repeated dismal strategic and tactical performances by blaming a legion of internal enemies. But the main point here is that he was almost single-handedly responsible for war taking an irreversible turn toward ruination of the old South and the implementation of emancipation, results that he completely opposed.
On July 11, 1862 Halleck was brought east and installed as General-in-Chief of the armies, a move that profoundly changed the course of the war and the basic nature of the conflict; by what his presence meant in Washington and no less by what his absence meant in the west.