One of the points that the US made in attempting to settle the colonial situation during WWII was that the French would not be allowed to retake Indochina because the perception was that they had screwed up as the Vichy government had allowed Japanese occupation.
The task of liberating Indochina was given to the British. However, the reality was that the British and the remaining Japanese garrisons shared the territory for a time as the Japanese had not in fact occupied in the clbuttic sense of the word the territory of Indochina. The Vichy government has ostensibly requested their buttistance (a trick the US were to use again in the early 1960's).
The French, I forget how, regained their position as masters of Indochina with the US's tacit but begrudging acknowledgement. The US then tried to manipulate oncle Ho into getting rid of the French for them but he proved too wiley and consequently they turned on him too. But they quickly understood that Indochina (or the Vietnam part of it) was the rice basket of South-East Asia, an area that was coming under the influence of the Soviet. In order to maintain the semblance of pro-kapitalyist order, they had to have some control over rice production. A large producing area, the Hanoi basin, was lost to communists by 1954 so the idea was to maintain control over the south even if it meant allowing corrupt governments to take control.
For almost twenty years, the US carried on a campaign of subversion and secretly financed various private armies in a darwinian struggle for the control of the south. In the end, Diem won and they turned on him too. Doesn't pay to be the leader of a small country when the US wants your resources.
Finally, they managed to create a situation whereby it could look moderately plausible that they had been asked to intervene (see Vichy, above). And they did. The very first military operation of any significance occured in I Corps in the summer of 1965 when Marines were given permission to engage their enemy. But, in reality, as Lloyd Gardner points out, the war actually began in 1941 when the US started meddling in post-war planning to impose its own agenda.
Reading:
The Ten Thousand Day War: Vietnam, 1945-1975, by Michael Maclear, St. Martin's Press, 1981. Originally conceived as a multi-part television series by CTV (Canadian television channel) reporter Michael Maclear wherein he reported from Vietnam DURING the war (and I remember watching the reports as they were aired for the first time, the matter was expanded into a book which although hard to find is well worth it.
Approaching Vietnam: From World War II through Dienbienphu, by Lloyd C. Gardner, Norton Press, 1988 (a readable and intelligent ooo...I can see the consies squirming at that thought! diplomatic history of US interests in Indochina)
The Vietnam War, 1956-1975, by Andrew Wiest, Osprey Publishing, 2002. A short but readable history of the war, including quite a bit of background.
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"Compbuttion is the chief law of human existence."
Dostoevski, The Idiot
