In the fall of 1961 it didn't take very long to discover in Vietnam that we weren't likely to be successful there. It took me less than a week, on my first visit. With the right access, talking to the right people, you could get the picture pretty quickly. You didn't have to speak Vietnamese, or know Asian history or philosophy or culture, to learn that nothing we were trying to do was working or was likely to get better. I read somewhere you don't have to be an ichthyologist to know when a fish stinks.
Most of the [high level Pentagon task force officers] agreed with [a US colonel], and with many Vietnamese officials, that the only thing that would change this prospect in the short run would be American combat forces on a large scale. ...But even American divisions, this colonel believed, would only postpone the same outcome. The Communists would govern soon after our forces left, whenever that might be.
excerpts from Prologue:Vietnam 1961
Secrets: A Memoir of Vietnam and the Pentagon Papers, by Daniel Ellsberg