Have you ever heard of the Khmer rouge in Cambodja, and how north Vietnam played a fundamental role establishing it?
IIRC Cambodia is the most bombed country in history.
...in response to the Khmer Rouge's attacks on Vietnam.
https://en.m.wikipedia.org/wiki/Cambodian%E2%80%93Vietnamese...
> which was supported by China and the US.
Vietnam was concerned Cambodja's regime was too China-friendly, but the millions being killed under the banner of advancing socialism did not featured as a pressing concern by neither China nor Vietnam.
There were, of course, geopolitical calculations on all sides, which is why the United States and China supported the Khmer Rouge. I don't think moral revulsion alone often leads any government to declare war on another.
Given that communism actually won in Vietnam, we don't even have to work with hypotheticals. There were certainly deaths but nothing to the level of the death toll American military power exacted on the populace.
Regarding the word intervene what I meant is that I believe it is not a good descriptor of what the US did. Makes it sound like some kind of spontaneous humanitarian mission rather than them undemocratically propping up a failing state.