Are you actually trying to tell us France did not repossess Vietnam in 1945/46...You are deluded if you think so. They did. Its a fact.
I have a pretty good knowledge of this particular period of history.
If I could say honestly, your understanding of this part of world is superficial.
There is a book written by Graham Greene on this period, The Quiet American, it was pretty close to describing the role of the USA in kicking the French out of Indochina.
The proper Vietnam war happened after 1956 and intensified under JFK. France has left by then, its main presence then was just the embassy in HCMC and a few privately run schools.
Dien Bien Phu was the last attempt to keep Indochina under French control.
Don't try to link the war of independence to the war of re-unification. They were fought for different reasons, on a very different scale and involved very different armies.