You mean except for the state of Virginia right?
Up to now I've been posting via my Iphone, which has limited the depth of discussion. Let's see if I can't do better with a keyboard.
You might note that a large percentage of the population in the northern states were perfectly happy with the secession by the South, but I'll get to that in a second.
Secession in itself is not aggression, certainly not in the true meaning of the word. Obviously it was the triggering event to all else that followed, but then so too was the Declaration of Independence the triggering event for the American Revolution (secession) from the UK. King George III and Lincoln were both faced with a people who were declaring self-determination and they both had the option to accept that self-determination or try to repress it. They both chose the latter, with Lincoln obviously being more successful than King George III.
The underlying problem with the South's position was its own hypocrisy of claiming the supremacy of self-determination, while simultaneously being a slave state. I'd call it moral nullification.
Very few in the South wanted war, as they knew who and what they were up against. When peace was no longer an option, the Southern war strategy was to force the North to accept the status quo of a split nation, not to reunite the nation under Southern control.
Now let's look at what did and did not light the fires of war in the North. There existed a small, yet strident percentage of the population in the North, going back to at least the 1830s, who wanted a war of domination over the South to end the evils of slavery; however, a war to end slavery wasn't a very popular notion. It was believed in the South, and rightfully so, that this faction was bent on forcing an end to slavery via excluding expansion westward of slavery (making the Old South an isolated minority that could be voted out of existence). That faction had a strong ally in northern industrialists who were pushing tariff laws that were detrimental to the South.
Southerners were stupid to secede when they did, and how they did. They did it on the presumption that the election of Lincoln was a de facto power move against them. But a peace time Lincoln wouldn't have had the power to act on his motivations in the way the South feared, and the Northern population certainly did not support a war to free the slaves. So the South provided the opportunity for those wanting war in the North to get their way.
Having said that, the abolitionists in the North both welcomed and feared Southern secession. On one hand it offered the catalyst to the war they desired, but on the other hand they feared that the Northern population would accept secession, leaving slavery in place.
You point to Southern provocations leading up to successions, but your provocation is another man's warning. There were clear indications that a coalition of commonality in the south was increasingly unhappy with their minority status. Why? Because they saw an increasingly powerful federal government that was soon going to have the ability to force them to comply. We might like that power in regard to slavery, but not many of us are enjoying all of its other manifestations.
Both the South and the North justified the war, once it started, under false pretenses to get the bulk of their respective populations to get behind it.
The South trumpeted the moral high ground of state's rights and self-determination, but rather hushed up the issue of slavery as the underlying issue that they were exercising those rights over.
The North rather invented the notion of an unbreakable union, which isn't Constitutionally mandated. It fired nationalism in a population that had already embraced a concept of continental manifest destiny. This was needed, because abolitionists had failed to get any considerable traction over the previous 30 years.
So that brings us back to the South making bad decisions. They ascribed the motivation of the abolitionists to the vast majority of Northerners, thus they presumed that an attack was coming. They started raising an army and fortifying their borders. They failed to nurture the more general feelings that existed through most of the North.
Lincoln was faced with a problem after secession, i.e. There wasn't a war. Everyone had gone to their corner, but no one was shooting. Having a deeper understanding of the populations general sentiment, Lincoln knew that he couldn't get popular backing for a war of conquest over the South. He needed something more, and the harbor forts located in the South gave him that opportunity. He ordered his forces to hold them with the hope that they would be attacked. Both sides were waiting for the other to fire the first shot.
Lincoln set in process an ultimatum for the South, which the South stupidly jumped on. He would resupply the forts and defy the South to do anything about it. The South would have been wise to find ways to peacefully stop that military build up, such as floating barricades across the mouth of the harbor, but they instead saw the gauntlet that was tossed down as an insult to their honor, which had to be immediately answered. Sumter was fired on.
So Lincoln got what he wanted, which was something he could trumpet as a Southern attack. An immediate call for 70,000 volunteers went out, to march and Richmond and crush the rebellion.
So who started the war and who wanted the war? Abolitionists were about the only ones who really wanted a war. Yes, once the fever and propaganda kicked up, everyone was gleefully talking about kicking the other sides collective butts, but those feelings were not initially there.
When I say "War of Northern Aggression" you immediately presume that I mean that the South was lilly clean and morally justified, and in that you are incorrect. I like the term because it best describes the 30 years leading up to war and the underlying motivation for not having a peaceful secession.
You might be happier if I modified it to "War of Northern Aggression Against Slavery", which is also true and even more descriptive of the decision makers, although the reality was that most of the North didn't fight to end slavery, but to protect the Union, which was not a justifiable moral position.
The incorporation of slavery into the new United States was a fundamental moral paradox that led to war, and that war created a mindset that fostered an ever growing federal power. In short, the solution to one problem created another. The war was ostensibly fought by the North to protect the integrity of the United States, but one of the far reaching outcomes was to destroy the union as it had been conceived in 1787.
If that is all a bit much, wait until I tell you about why we shouldn't have been involved in WWI. The concept of "preserving the union" was an odd war cry.
Did there? Was there? Garrison and other abolitionists would have been happy dissolving their connection to the slave states. They thought of the federal government as part of the problem, not as a military arm of their movement.
John Brown, a full generation after 1830, wanted to arm the slaves and wanted the slaves and their allies to fight a war of liberation. He wasn't looking for any federal war of domination over the South, so far as I know.
To be sure, abolitionists had much animosity against the South, and many people prophesied an eventual war between the sections, but I don't see any long-held desire for a war of destruction against the slave-owners.
That looks a lot like a case of reading what eventually did happen back into the intentions of people years before. But -- as an example -- we could have very hostile feelings towards the Communists and they towards us without either side wishing for a war of destruction or annihilation against the other side.
In conflicts, both sides are often holding their own. When one side crumbles or is crushed you may think it was all part of a plan or the intention of the other side, but often enough they just have trouble keeping up their end of things.
So that brings us back to the South making bad decisions. They ascribed the motivation of the abolitionists to the vast majority of Northerners, thus they presumed that an attack was coming. They started raising an army and fortifying their borders. They failed to nurture the more general feelings that existed through most of the North.
Now that, that is a starling aperçu.