If France's Maginot Line was nearly impenetrable why did they risk their survival by leaving a gap? Why did France think the Ardennes was impassible? Assuming it was, would France and Belgium have been able to halt the Wehrmact?

by Naugahyde1453

As I understand it, the French strategy in World War II was to engage the Wehrmacht defensively on Belgian fortifications. The best case scenario is that the line is held and thus France is unmolested at the cost of many lives. The worst case scenario is that the defence is overrun by the Wehrmacht and France is invaded.

Considering this, why would they not play it safe and simply extend the Maginot Line to the ocean?

Additionally, what made the French believe the Ardennes was impassible by the Wehrmaht and what was it about the Wehrmacht that made the French so wrong?

Finally, if the Ardennes was indeed impassible by the Wehrmacht, would it really have mattered; would the French and Belgian forces have realistically been able to hold off the Wehrmacht?

DanKensington

There were other considerations at play. u/kieslowskifan has an excellent overview on the line and Belgium's role in the defence. On the matter of the Ardennes, they also address that in this post; see also this post from u/hesh582 on getting through the Ardennes.