You're referring to the 1978-79 invasion of Khmer-Rouge-governed "Democratic Kampuchea" by (the by-then unified) Vietnam, about which you're absolutely correct.

In contrast, I was referring to the 1970 North Vietnamese invasion of Cambodia, which led to the U.S. incursion there, which in turn touched off protests in the U.S., including the one at Kent State.

> [Referring to South Vietnam:] a military dictatorship that was only able to maintain power because we supported it really wasn't a legitimate government no matter how you slice it.

A lot of Vietnamese immigrants to the U.S. would strongly disagree with you. Drive around the Little Saigon area in Houston (or numerous other cities). You'll see plenty of South Vietnamese flags flying. This, even though it's been nearly 40 years since North Vietnam completed its conquest in April 1975.

There's a selection bias at work here, of course; the people who fled South Vietnam and came to the U.S. were, by and large, people who were aligned with, and benefited from, the South Vietnamese government.

Still, it speaks volumes that so many South Vietnamese fled -- by small boat, and who knows how many of them drowned at sea or were killed by pirates.

The North Vietnamese had heavy logistical support from the USSR and China. After Watergate and Nixon's 1974 resignation, the U.S. Congress -- controlled by the Democratic Party, whose base by then was heavily influenced by left-wing "peaceniks" -- cut off logistical support for the Saigon government. (Foreign policy wise, the Democratic Party of today is very, very different from that of the 1970s.) The cut-off of U.S. support was pretty much game over for South Vietnam.

Some argue that the quick collapse of the Saigon government suggests that the government didn't enjoy broad popular support among the South Vietnamese people. Another possible explanation is that the South Vietnamese were tired of war and saw no point in sacrificing their lives in the face of overwhelming military force.

I do think there's considerable room for argument that, after the Japanese surrender and evacuation from Vietnam in 1945, the U.S. should have backed Ho Chi Minh and his Vietnamese nationalists, instead of supporting a return of the French colonial rulers (who were booted out after losing the French-Indochina War 1950-1954). There's also no question that the Saigon government was far from ideal.

But I don't think there's any dispute that --- on the whole --- the (Communist) North Vietnamese government was far more systematically brutal than was the South. Indeed, systematic brutality seems to be a common and recurring theme among Communist governments. Which goes to my original point.