I'd have to go look it up, but as I recall, we were already sending advisors...very few of them...and way way way quietly as early as '56.<quoted text>
What was Eisenhower's involvement? My personal recollection is that the US did not start sending advisers over there until 62 or so. I had friends whose older brothers were advisers.
Eisenhower effectively stayed out of it but IIRC the US part in it was primarily paying France to stay there and deal with it. It was still French Indochina. We were propping up the French.. The French wanted either the old colonialism or they wanted out.
If they left and no one stepped in, what became S. Vietnam (because it wasn't really a nation as such...more like districts or provinces) would have been taken over by N.Vietnam. It would have been the one single Vietnam that HCM wanted (and that it became anyway).
Also, remember the whole anti-communist hysteria here at that time, Mc Carthy, et.al., and they were all convinced that if Vietnam fell, Cambodia, Laos, Thailand,-you know, the "domino effect"- and the USSR would step in to spread communism across the world through SE Asia, across the Pacific and right on to Main Street, USA.
Also remember that I only paid as much attention to that class as I needed to in order to get my A. I only heard about 2/3 of whatever he said. <shrug>