The French’s miscalculation at Dien Bein Phu was that the Viet Minh were not capable in moving their artillery into the terrain, they were. The US never promised the use of nuclear weapons in Indochina in 1953-54. Every serious book I have read on this conflict, and I have read many, have never mentioned this promise. The thought was brought up and swiftly shot down by Eisenhower.
There was a two hour program about Dien Bein Phu maybe10 years ago. It was on one of the History type channels and gave a very detailed account of the battle.
The French knew they were getting surrounded and by a vast number, something like 50 to one. They had been promised American aid and that was the place to wipe the NVA out. That included nuclear weapons if necessary. Even if nuclear arms were not used, American jets would cover the mountain tops with napalm. Lyndon Johnson was the one who put a stop to it, then with the story out, we just left them to die.