That line is on of the reasons I draw parallels between Vulcan and Japan. After WWII Japan went from enemy to staunch ally and was occupied by US forces for several years after the war.
When you combine that with the Romulans as surrogate Chinese, that makes craptons of sense.

Well they pretty much ignored that line in future TOS episodes as well. Turning the Vulcans into pacifists and philosophers. I think part of that was the time in which TOS was made and Spock becoming a darling of the counter-culture (or a segment of the counter-culture)
I'd never thought of that before. Great point!
I'm enjoying this thread immensely, but what I just read either reveals that McCoy's knowledge of history is flawed (because he is drunk?) or a continuity problem. Here is the dialogue from "The Immunity Syndrome":
Spock: True. It is also true they never knew what was killing them. Their logic would not have permitted them to believe they were being killed.
Kirk: Explain.
Spock: Vulcan has not been conquered within its collective memory. The memory goes back so far that no Vulcan can conceive of a conqueror. I knew the ship was lost because I sensed it.
I've always found Spock's first line so... awkward. "Logic would not permit them to know they were being killed." That's just silly.
Star Trek had continuity but it wasn't the ridged "every thing counts" continuity that some fans would like. They were more than willing to toss out ideas that didn't work or look for ideas that worked better. The first half of Season One is littered with abandoned ideas. That doesn't make them hacks, it shows they were professionals.
"A foolish continuity is the hobgoblin of little minds".![]()
This. The idea of continuity is what builds the impression of a real universe; changes of a minor nature, in relatively minor amounts, are reconcilable until they reach a certain "critical mass." I believe the makers of TOS understood this, as did viewers.
There are shows which ignore all continuity and realism and do different things from week to week without caring, and shows which make a marked effort towards continuity and realism. TOS was definitely the latter.