In the book The making of Star trek II, the wrath of Khan by Allan Asherman: What happened in 1864? I'm not " a student of American history", thanks
It's the penultimate year of the American Civil War, but glancing over timelines and summaries, I don't see any specific event that's particularly applicable to the film in that year. For instance, the Monitor and Merrimack fought in 1862. Aside from the general concept of "things that used to be on the same side are now fighting each other," I'm stumped by what Asherman could be referencing.
https://en.wikipedia.org/wiki/1864_in_the_United_States yeah, maybe that Asherman guy didnt know as much history as he thought the did
I always took Asherman's 1864 reference to mean TWOK's battle between two Federation starships—a civil war, if you will—as opposed to the Enterprise facing off against an alien (Klingon, Romulan, etc.) vessel.
Might 1861 also imply a newer class of starship? That said, the civil war issue - pointing to a specific year and battle of importance therein as a semi-subtle nod (or even in a hope that the kiddies in the audience would run down to the library like how they otherwise never do?) - makes more sense than the number being a vague and superficial number as Khan was never in Starfleet so it's not a civil war within the Federation. Khan could be Klinglan or Romugon and it wouldn't make a difference.
My point was not that it's a literal civil war but rather a symbolic one, as both the Enterprise & the Reliant are Federation starships going head-to-head. The fact that Khan and his followers aren't Starfleet officers has nothing to do with it.