Probably the best documentary made over the French defeat in 1940.
Unfortunately for many here, it is in French and I can't find a sub version.
The document is from the 70` and goes into details of the reasons why France has been defeated son badly in that short period of time.
1- It interviews politics and generals (dead today) that were there during those events and provide really interesting insights over the politic and military strategy of France in 1939-1940 which lead us into this big failure. It describes quite well how the French military head was completely outdated and that before a failure of the army, it has been a failure of its head.
2- It shows the general feeling of French people in 1939 and the fear and sequels the 1st world war had left to those people. You can have a perception of egoism looking at how they try anything they could (including abandoning allies countries) just to not go in war.
After the war and until now, French are still thinking they lost the war because the German army was better, had better tanks, better planes better anything. And this feeling has been promoted all this time by the French politic and military class in order to mask this other reality, the failure of the French elite. French tanks were better than German ones, French planes were good enough to fight German ones and French soldiers were well prepared to fight. But all of those has been badly lead all this time.
This doc is quite unique and if someone has the capacity to sub it in English, it would probably have a large audience.