The Vietnam War then resulted, not because the North Vietnam
> government was threatened with invasion by the U.S., but because the
> NV government was simply determined to obtain sovereignty and control
> over South Vietnam, and to do so initiated an aggressive (and quite
> vicious) war to do this -- right?
Not really. There is a rather compact summary of how that got started in the Wikipedia article on the history of Vietnam. The origins were fairly complex, involving not just the two governments, but groups in the south that had not been suppressed and foreign involvement from the US, UK, France, and the Soviet Union.