 Yet just as had been the case in the zones of the XXI Corps and the XV Corps, it was less the hard fighting of the VI Corps that would determine when the Siegfried Line would 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.