It seems that the smart move by the Confederacy would have been to just avoid open conflict at all costs. The notable quote by Confederate secretary of state Robert Toombs about an attack on Fort Sumter,
"Mr. President, at this time it is suicide, murder, and will lose us every friend at the North. You will wantonly strike a hornet's nest which extends from mountain to ocean, and legions now quiet will swarm out and sting us to death. It is unnecessary; it puts us in the wrong; it is fatal."
makes it seem that opinion was not unpresent. How widespread was the opinion that war should be avoided at all costs? Was there any hope that the confederacy could just wait it out and then just obtain a significant degree of autonomy from the union? Was the union set on the mindset of going to war to reign back in the southern states, or if the confederacy had played their cards right, was calling the unions bluff on their willingness to go to war a possibility?
On a somewhat separate note, what exactly did Jefferson Davis mean in this quote of a portion of his farewell address to the senate upon the secession of Mississippi?
The communities were declaring their independence; the people of those communities were asserting that no man was born--to use the language of Mr. Jefferson--booted and spurred to ride over the rest of mankind; that men were created equal--meaning the men of the political community; that there was no divine right to rule; that no man inherited the right to govern; that there were no classes by which power and place descended to families, but that all stations were equally within the grasp of each member of the body-politic. These were the great principles they announced; these were the purposes for which they made their declaration; these were the ends to which their enunciation was directed. They have no reference to the slave; else, how happened it that among the items of arraignment made against George III was that he endeavored to do just what the North has been endeavoring of late to do--to stir up insurrection among our slaves? Had the Declaration announced that the negroes were free and equal, how was the Prince to be arraigned for stirring up insurrection among them? And how was this to be enumerated among the high crimes which caused the colonies to sever their connection with the mother country? When our Constitution was formed, the same idea was rendered more palpable, for there we find provision made for that very class of persons as property; they were not put upon the footing of equality with white men--not even upon that of paupers and convicts; but, so far as representation was concerned, were discriminated against as a lower caste, only to be represented in the numerical proportion of three fifths.
I am a little confused on if Jefferson Davis was speaking derogatorily about the blacks, or if he was calling out the hypocrisy of the North, in that the three fifths compromise effectively established the blacks as non-persons.
Sorry it's taken me some time to get to this.
/u/thelastvortigaunt has given (what I think of as) a good answer, but it is perhaps incomplete.
I suppose the question I'd put to you is this.
Let's pretend Lincoln backed off at Sumter for whatever reason. (This is a huge 'what-if' that I'll return to.) Let's suppose that fire never broke out, the Confederacy set up its government, and the countries continued on a trajectory of some manner of co-existence?
Now, given that we are in Alternate History Land, how long would it take for the competition between nations to erupt into war?
Given that the Union would go on to meddle in Mexico and Cuba pretty quickly after the war, it seems reasonable to assume some conflict would have erupted. In this what-if guessing, I'd give it twenty years and feel generous.
But the thing is, Lincoln didn't back off at Sumter, because Lincoln believed strongly in the Union, and he represented a fairly mainstream opinion (if a hotly contested one) in the North.
And from a certain point of view, you can squint and see that the 'what-if' scenario is exactly what happened. Two governments were set up, and then the countries picked a fight with one another.
Call that inevitable if you like. To me, though, (and to thelastvortigaunt) the word doesn't help us that much.
What actually happened is that various leaders had advisors and made important decisions. You're right: the opinion that attacking Sumter was a mistake was 'not unpresent'!
Once secession was declared and the Confederacy formed, yes war was inevitable.
Step one as a new nation is to secure national territory, that means securing forts and arsenals. Federal troops were surrendering left and right with no problems.
Fort sumner was a fort in a major port, they refused to surrender, so the CS army followed up on their promise and forced a surrender. The northern response to the attack was calling up 75,000 volunteers to put down the south. 4 more states joined the confederacy because of this and a call for 100,000 volunteers to defend the south. So started the war.
Now if the federals surrendered with out a fight then the confed would have continued to secure the territory, build up the army and further work on foreign recognition.
That means the north would have no power to keep the union together other than militarily meaning either recognize the new nation or put it down by force.
"Inevitable" is a difficult word to work with -- all we can really do is speculate about alternate situations.
Do we have any primary source documents from Lincolns cabinet regarding a situation in which the south refused to initiate the first strike? If so, was there any talk about possibly engaging in a false-flag attack in order for the north to get the justification they needed to attack?