 Thus, hardly had the American combat command begun to move early on 20 March to exploit the 63rd Division's penetration when the 45th Division of the XV Corps also advanced past the last pillboxes of the Siegfried Line near Zweibrücken.During the night of the 20th, the rest of the SS "korps" also began to pull back, and the momentum of the 3rd Division's advance picked up accordingly.The German problem was to get the survivors of both the LXXXV "Korps" and the XIII SS "Korps" through the Pfaelzer Forest despite three dire threats