problem remained of staggering proportions.
The area in which the Army Group B would concentrate its forces, equipment, and supplies was delimited on the south by the Moselle River and had as its base the Rhine crossings stretching from Dusseldorf to Koblenz. On the north there were actually two limits. That farthest north ran from the Rhine west on the axis Munchen-Gladbach and Roermond. South of this line Allied intelligence officers watched, as they were intended to watch, the daylight, only half-disguised, movement of German troops and supplies. Farther south a second and true limit defined the main concentration area. Here the line extended from Bonn, through Euskirchen, to the front north of Monschau. The trick, then, would be to effect a large and secret concentration south of this second line while at the same time preparing to sideslip the forces from the north into this sector in the last hours before the attack.
The first problem of organization was that of rail transport.  Troops, tanks, and guns had to be brought from East Prussia, Poland, Austria, the Netherlands, Denmark, and Norway. Fuel and ammunition had to be hauled across the exposed Rhine bridges and unloaded quickly and quietly at the Eifel dumps. A number of divisions, in particular those assigned to the Sixth Panzer Army, would have to be shuttled from the battle front back across the Rhine to training and refitting areas, then be moved across the Rhine again and into the concentration zone.
Probably no railway system in the world was better able to handle this tremendous task than the Reichsbahn (the German State Railroads). It had been modernized on the eve of the war, was a model of efficient management, and, through a program of systematic looting, had more than replaced the rolling stock lost to air attack. The cars and the locomotives in large freightyards, as many American soldiers will
remember, read like a European railroad gazetteer. Militarization of the German railroads was complete. The German Army had been the first in history to employ railroads for a greatstrategic concentration, and the successes of 1870 had led to a tradition in General Staff thought and trainingwhich looked to the rail system as the primary means of strategic concentration. The rail lines along the Rhine and west of the river had been located in accordance with military desires. The Eifel branches had been constructed inpreparation for the First World War, then had been reinforced for the campaign of 1940. But there was more thanthe tradition of the great General Staff to dictate this reliance on rail: Hitler's scheme for a military superhighway system, the Reichsautobahnen, had been cut short by the war; the Allied attacks against motor fuel production had depleted German stocks, although hardly to the extent that Allied intelligence estimated in the autumn of 1944.
The major threat, of course, was the overwhelming superiority of the Allied air forces and their ability, no longer effectively challenged by the Luftwaffe,
 The best study on German rail movements and explanation of pertinent German sources will be found in Charles V. P. von Luttichau's manuscript, German Rail Communications in the Ardennes Offensive, 194445 (1952). OCMH. See also the OB WEST KTB and Anlage for the supply build-up prior to the attack.