Great work!
To simplify (and considering the California problem): By the Constitution, the People of the United States through Congress OWN and are sovereign over forts, magazines, dockyards, arsenals, post offices and post roads, and other needful buildings located in any State considering secession.
THEREFORE: A seceding state must either NEGOTIATE a satisfactory agreement with the People of the United States regarding our property and the utilities that flow from sovereignty over same (e.g., naval basing at San Diego, movement of mails from San Francisco over Interstate highways, etc), OR they must seize those things and claim right of conquest according to the Laws of War.
South Carolina chose the latter, and had to accept the outcome.
Exactly, and remember those folks were all Democrats.
And what is the first rule of being a Democrat?
Right: always blame Republicans for your own misdeeds.
That's why Fort Sumter is Lincoln's fault, or Bush's fault, or Trump's fault, whatever, it doesn't really matter so long as Democrats themselves don't shoulder the blame.