Final answer:
The third German army bypassed the French Maginot Line by attacking through the Ardennes Forest on the French-Belgian border. This strategy was part of the broader German offensive against Western Europe, which included a rapid blitzkrieg attack that quickly overwhelmed French and British forces.
Step-by-step explanation:
The third German army attacked through the Ardennes Forest, a region on the French-Belgian border. This move by the Germans effectively circumvented the Maginot Line, France's heavily fortified border defenses, which the French believed to be impregnable. The German forces utilized a blitzkrieg strategy that involved a rapid advance of tanks and artillery, catching the French and British forces unprepared and driving them back.
Previously, in April, Germany had invaded Denmark and Norway, and then on May 10th, they launched their offensive against the Netherlands, Belgium, and France. The German success in bypassing the Maginot Line is seen as a critical failure in French military strategy, leading to significant territorial gains for Germany in Western Europe during World War II.