German POWs after Battle of Aachen during World War II

The transcript describes a dire situation for German forces as they face a crushing defeat. The enemy has advanced onto German soil, with the potential to reach Berlin. The Siegfried Line, once a strong defense, has proven ineffective, allowing enemy forces to flood into the country.

What does the mention of the Siegfried Line imply about the defense?

What metaphor is used to describe the overwhelming situation faced by the men?