To be fair, many of the defenders of Dien Bien Phu were colonial troops, mostly Algerians, and the Legion Etrangere was, by definition, not composed of Frenchmen, although I believe some of their officers were.
But the bulk of the army was French, and included veterans of the Free French units of WWII.

Still, the accounts of the battle make stirring reading, and it is clear they conducted themselves with honor. In fact, their cruel last orders, radioed in after the airstrip was unusable, relief or evacuation impossible and their ammunition running out, was to resist until they could no longer. There was to be no formal surrender.

The walking wounded were manning crew-served weapons, and other casualties, having been evacuated earlier for treatment, were being parachuted in. They had volunteered to serve one last time with their units, knowing full well what their fate was. Not only was their defense determined and disciplined, but they even conducted numerous sorties, inflicting many casualties on their foes and capturing thousands of prisoners.

The site they had chosen to make their stand was at the intersection of numerous supply routes that provided their Viet Minh enemies with materiel. Situated in a small plain surrounded by mountains, the French believed they could interdict enough supplies to cripple their enemy's campaigns. What they had not anticipated was a masterful logistic effort by the Vietnamese which surrounded the French force (essentially, a reinforced division) with over a hundred thousand men and thousands of artillery pieces and anti-aircraft guns. Once the weather made air support impossible and the airstrip was knocked out, they found themselves at the bottom of a huge bowl with the enemy raining heavy fire (from American 105s captured by the Chinese during the Korean war) day and night. The siege lasted for weeks, but its outcome was never in doubt.

It is estimated that only about half of them survived after it was all over, an amazing casualty rate for any army. Most of the survivors died of their wounds or in prison camps afterwards. As is always the case in war, it was a stupid, pointless horrible waste, but even in defeat, it was also their finest hour.