The fact remains that all wars are started with military conflict. If troops and citizens are not invading territory and/or shooting each other, it gets labeled a phoney war as during the Wehrmacht annihilation of Poland of WWII, while a small German force faced a much larger French army on that border, a "Sitzkrieg."
This thread is about what caused the war. Very simple.
The ACW supposedly started April llth 1861,with the bombardment of Ft Sumter by the South Carolina militia under Gen. Beauregard. However,....
That followed the actual first shots fired by cadets from The Citadel against a hired civilian steamer April 9th which prevented supplies and reinforcements from reaching the fort's garrison. The ship turned back without losses.
That bloodless repulse is still not cited as the cause of the ACW, probably because no loss of territory or life resulted...or federal installation.
Not enough for propaganda purposes to prosecute a war.
Furthermore, a federal fleet including large warships and troop transports was dispatched 6 April converging before midnight April 11th off Charleston's port intending to force their way through the harbor to reinforce Ft Sumter.
The surrender of Ft Sumter, again with no combat losses, was the bloody nose which the war mongers in Washington DC used to inflame a war effort.

[ although the garrison managed to kill two of their own when a cannon firing a salute exploded]
The surrendered Union soldiers were allowed to return on a supply ship to New York City where they were honored with a parade.

again.
Fort Sumter was the Union's installation by which the federal government intended to prevent Charleston trade with Europe unless duties were collected by Union federal agents.
That is "taxation without representation" for which the colonies went to war against England and won their independence.
The Confederacy was fighting for its independence and free trade.
There were always socially and politically prominent citizens who wanted to prevent the loss of their property in slavery...in every country that abolished it.
So what?
The Southern states' succession statements did not cause the ACW, no matter how angry propertied slave owners fulminated against the Northern insults and nullification of the US Constitution and laws which protected the rights of slaveowners.
The Union armies which marched into the South and Union fleets which blockaded Southern ports did not do so with the proclamation of intent to free slaves. After all there were 5 slave states still within the Union.
The Union was a slave holding nation and protected their slave owners throughout the ACW:

Maryland

Delaware

West Virginia

Kentucky

Missouri
Let there be an end to attacking the Confederacy for having its "peculiar institution."
The federal government did proclaim their intention to prevent succession and blockaded South ports.... to prevent the freedom of the Confederacy to trade with England and France without paying tariffs to the federal government.
Cui bono? (Who benefits?)
Try.....the Northern industrialists and moneyed interests such as Wall Street bankers.

Today we call such collusion, "crony capitalism," although it used to be described as economic fascism or corporate socialism.
BG Ross McDaniel
2nd Bde, 3rd Div, III Corps, AoG, CSA
"Southern Bid for Commercial Power"
It does not require extraordinary sagacity to perceive that trade is perhaps the controlling motive operating to prevent the return of the seceding States to the Union, which they have abandoned. Alleged grievances in regard to slavery were originally the causes for the separation of the cotton States; but the mask has been thrown off, and it is apparent that they people of the principal seceding States are now for commercial independence. They dream that the centres of traffic can be changed from Northern to Southern ports. The merchants of New Orleans, Charleston and Savannah are possessed with the idea that New York, Boston, and Philadelphia may be shorn, in the future, of their merchantile greatness, by a revenue system verging upon free trade. If the Southern Confederation is allowed to carry out a policy by which only a nominal duty is laid upon imports, no doubt the business of the chief Northern cities will be seriously injured thereby.
The difference is so great between the tariff of the Union and that of the Confederated States, that the entire Northwest must find it to their advantage to purchase their imported goods at New Orleans rather than at New York. In addition to this, the manufacturing interest of the country will suffer from the increased importations resulting from low duties...The ...(government) would be false to all of its obligations, if this state of things were not provided against. -The Boston Transcript 18 March 1861
"...It is that you may have an opportunity of cheating us that you want to limit slave territory within circumscribed bounds. It is that you may have a majority in the Congress of the United States and convert the Government into an engine of northern aggrandizement. It is that your section may grow in power and prosperity upon treasures unjustly taken from the South...You desire to weaken the political power of the southern states; and why? Because you want, by an unjust system of legislation, to promote the industry of the New England states, at the expense of the people of the South and their industry." -Jefferson Davis, from a speech before the ACW
“Any people anywhere, being inclined and having the power, have the right to rise up and shake off the existing government, and form a new one that suits them better. This is a most valuable, a most sacred right—a right which we hope and believe is to liberate the world. Nor is this right confined to cases in which the whole people of an existing government may choose to exercise it. Any portion of such people, that can, may revolutionize, and make their own of so much of the territory as they inhabit.”
Abraham Lincoln in a speech before Congress on January 12, 1848