You might be interested in some previous threads on the Fall of France:

• Why did France fall to Germany so quickly in wwii? - 13 comments, over 1 year old.
• The commenters here give a summary of the expectations and plans of all of the involved forces, including comparisons to the WWI invasion of France through Belgium.
• If Germany at the start of WWI headed to France by way of Belgium, why did France create the Maginot Line in the 1930s? - 3 comments, over 2 months old.
• A summary of the role and effectiveness of the Maginot Line which also leads into the German attack through the Ardennes in WWII.
• How were the Germans able to so easily pass through the Ardennes when the Allies considered it impassable? - 3 comments, over 9 months old.
• Here's a summary of the importance of German planning right up to their WWII invasion of Belgium and their use of the Ardennes.
• "Allied generals in World War II felt [that the ardennes] was impenetrable to massed vehicular traffic and especially armor". Why was that, and how did the Germans circumvent the difficulties? - 9 comments, over 6 months old.
• The commenters here explore in detail the roles of the Maginot Line, the Ardennes, German and French strategic planning, doctrine, and funding which changed greatly between the wars.