be pierced than it was the rampaging thrusts of the Third Army's XX Corps in the German rear. The divisions of the VI Corps had been probing the pillbox belt less than 24 hours when General Walker, leaving the task of gaining the Rhine to the 12th Armored Division and of actually capturing Kaiserslautern to an infantry unit, turned the 10th Armored Division south and southeast into the Pfaelzer Forest. By nightfall of 20 March, two of the 10th Armored's columns stood only a few hundred yards from the main highway through the forest, one almost at the city of Pirmasens on the western edge, the other not far from the eastern edge. A third was nearing Neustadt, farther north beyond the fringe of the forest. The 12th Armored meanwhile was approaching the Rhine near Ludwigshafen. Not only were the withdrawal routes through the Pfaelzer Forest about to be compromised but a swift strike down the Rhine plain from Neustadt and Ludwigshafen against the last escape sites for crossing the Rhine appeared in the offing. In desperation, on 20 March the Luftwaffe sent approximately 300 planes of various types—including jet-propelled Messerschmitt Me 262—to attack the Third Army's columns, but to little avail. Casualties on the American side were minor. Anti-aircraft units—getting a rare opportunity to do the job for which they were trained—shot down 25 German planes. Pilots of the XIX Tactical Air Command claimed another eight. In the face of the 10th Armored Division's drive, the word to the westernmost units of the XC Korps to begin falling back went out late on the 20th, and when the 42nd Division—in the mountains on the left wing of the VI Corps—launched a full-scale assault against the Siegfried Line late the next day, the attack struck a vacuum. Soon after dawn the next morning, 22 March, a regiment of the 42nd cut the secondary highway through the Pfaelzer Forest. A column of the 10th Armored had moved astride the main highway through the woods and emerged on the Rhine flatlands at Landau. Any Germans who got out of the forest would have to do so by threading a way off the roads individually or in small groups. By nightfall of 22 March, the Germans west of the Rhine could measure the time left to them in hours. In the Siegfried Line on either side of Wissembourg, Germans of Petersen's XC Korps