If it had just been South Korea against the North, without US aid? South Korea would have fallen, and stayed fallen. However, once we propped up the South and took them under our wing, we were beholden to keep them going or suffer the consequences elsewhere in the world with other allies. Moral hazards of doing what we did.

I’m still sort of ambivalent about Korea. They’ve always been a bit of an issue, there on the periphery of China, and not being Chinese. They’ve also been more than a little “off”, in that they’re not a particularly military culture, valuing their scholars and court more than their soldiers. It’s noteworthy that even when they were effectively resisting the Japanese back in the days of the Turtle Ships, the court in Seoul was doing all it could to undercut the admiral who was defending Korea. If a nation wants to survive plopped where Korea is, in between China and Japan, it had better be good at defending itself, putting a high priority on soldiers and defense matters. The Koreans, however…? Not so much, for much of their history. They’re kinda like that nerdy kid stuck in between the jocks and the greasers, constantly at the mercy of their more warlike peers.