Hitler's army was making the final preparations for its surprise attack.

From THE WAR, Episode 6:
NARRATOR: A few moments later, the enemy began to emerge out of the dense fog that shrouded the forest.

TOM GALLOWAY: And, 'course the Bulge broke right there. And as I say, when they fired the first round, it darn near hit me. From then on, it got worse. But they came barreling over there and just right into us.