Answer and Explanation:
Germany managed to invade France in 46 days. This surprised all of Europe who believed that the French resistance would be more aggressive, and could even defeat the Nazis.
One of the main reasons why Germany managed to conquer France was the use of the blitzkrieg. This was an innovative strategy for the time, when the German attacked its enemies with a series of coordinated attacks that united infantry, aviation and armored vehicles in a single point of the enemy's defense. To attack France, Germany used this strategy in the Ardennes, where the French army was completely cornered.
In addition, the German army made constant use of methamphetamines, which allowed soldiers to spend long periods of time without getting tired, promoting a progressive and fulminating attack.