[mrustow]

That is a good point, but not valid, IMO. To the Vietnamese (N. and S.), the interlopers were the Americans. The VC were fighting against them, the S. Viets were not; therefore, the VC had much more motivation.

But I'd always heard that the hatreds of a civil war -- countrymen killing each other -- were always more passionate than in any war against an external enemy.

[expatpat]

Yes, civil wars are intense, as you point out. However, there's no question that the US took over what started as a civil war, dominated the fighting agianst the VC, and thus changed it from a civil war into a war between the US vs. VC, with the S. Viets merely as camp-followers.