the weather and even included provisions for a stop-order to arrest the concentration in mid-flight should the weather suddenly turn fair. The concentration for Wacht am Rhein, already in progress when the U.S. Third Army reopened large-scale fighting on the Western Front, continued at a wobbly pace during the second and third weeks of November. Eventually the impossibility of relieving the attack divisions as scheduled and the delays wrought by the temporary commitment of units like the Panzer Lehr became so obvious as to brook no denial-even by Hitler. His postponement of the attack cannot be pinpointed, but the word probably came sometime after 23 November. On that date Model reported that of the armor slated for Wacht am Rhein only the four SS panzer divisions and the 2d Panzer Division had escaped premature commitment in the battles then raging. In Model's opinion-mark the datethe other divisions could not be readied before 15 December.
The area through which Hitler chose to launch his counteroffensive was, with the exception of the Vosges, the most difficult terrain on the entire line of the Western Front. It consists of two major parts, the Eifel and the Ardennes. Although the whole is strewn with the relics of castles and fortified churches, there had been little military history enacted within this area before 1914.  A straight line between Paris and Berlin will bisect the Eifel and Ardennes, but the movement of armies during the centuries normally had followed the easier roads going around this area: in the north via Liege-Maubeuge or the Flanders plains, in the south via the Metz gateway. On occasion the Ardennes and Eifel had been used by large forces for movement without fighting, battle being joined at the natural defense lines of the Meuse River west of the Ardennes, or the Rhine River east of the Eifel.
In 1914, as part of the Schlieffen Plan, three of the Imperial German armies marched from the Eifel through the Ardennes. Schlieffen had predicted that the French would react to the pressure of the heavy German right wing as it swung through northern Belgium by counterattacking into the flank via southeastern Belgium. It was an integral part of the famous plan, therefore, that the German right wing would be covered by an extension through southern Belgium and Luxembourg, and that the Ardennes massif would be used, if needed, as a bastion from which the French flanking attack would be repelled. A portion of the Second and all of the Third and Fourth German Armies did advance through southern Belgium and Luxembourg, the march through the main portion of the Ardennes being covered by the rapid movement of Richthofen's I Cavalry Corps. French reaction was slow and the tiny Belgian Army had been drawn away to defend Liege and Brussels. As a result the Germans marched across the main body of the Ardennes mass without a fight, the ultimate meeting engagements with the French on 22.
 The older military history of the Ardennes is narrated on a somewhat antiquarian basis in Revue Historique de l'Armee, 1955, IIe Annee, Numero 2. For the 1940 campaign see L. Menu, Lumiere Sur Les Ruines, Paris, 1953; also M. Fouillien and J. Bouhon, Mai 1940: La Bataille de Belgique, Bruxells, n.d.