> Like the original Maginot Line, this approach is about as effective a defense as a minor speed bump.

No

The Maginot Line forced the german army to go through the ardennes. It bunched up all their forces into a tiny crossing surrounded by valleys rivers and other such obstacle.

Two french spotter planes saw this and reported back. The report was regarded as spurious.

Had the report been acted on, the invasion of france probably would have failed.

France and britian had by far the best kit and numbers. However the french were in disarray politically, and the british weren't really integrating properly.

So the real reason barrier was the lack of joined up political thinking.