There are a lot of things a lot of people know which are not so.
The French purposely let themselves get surrounded by truly massive North Vietnamese forces knowing that America had promised to use nuclear weapons to kill all the NV at one time.
A U.S. Senator, Lyndon Johnson found out about it and forced the issue. The U.S. would not use the weapons and the French who fought as well as soldiers ever fought were all killed or captured.
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.
Where on earth did you come up with that story? Ridiculous!