The Allied decision to forgo any intensive attacks against the Rhine crossings gave this segment of the German rail system relative immunity during the build-up. The actual trackage and the freight yards, particularly those west of the Rhine, had no such immunity and would come under increasing attack in late November just when the concentration was swinging into full stride. Almost completely bereft of any friendly air cover, how did the Germans keep their rail transport functioning? Recall that the Wehrmacht had been forced to perfect the art of camouflage, that the traditionally severe German discipline functioned nowhere better than in the rigorous control of troop movement, and that the Reichsbahn was an integral member of the body military.
The first measure adopted to protect military trains from Allied observation and attack aimed at the utmost use of darkness and bad flying weather. All rail movement west of the line Bremen-Kassel-Ulm, a distance of 150-200 miles from the fighting front, was confined to those times when air reconnaissance would be stymied. A few exceptions, for purposes of deception, were permitted in the Aachen area. Control was decentralized and even the smaller rail stations were tied in to the main German weather service so as to wring the most mileage out of any local change in the weather. Supply trains were organized east of the Rhine and there allocated a particular line and army. Every effort was made to load down the branch lines, particularly when it became apparent that the Allies tended to concentrate on the main lines.
Train movement was very carefully controlled. The thick forests of the Eifel, plus an unusual number of rail tunnels near the chief supply dumps, gave considerable chance of concealment. Wherever possible the run was made to the unloading point and back to the west bank of the Rhine in one night. On double-tracked lines the movement was restricted to one-way traffic, then reversed. A host of small stations were given extra siding so that trains could be stationed serially all along the line and unloaded simultaneously. This system also permitted quick distribution to the many small, concealed dumps. Earlier it had been discovered that engine crews often were killed by Allied strafing while the locomotive remained intact. Special light armor plate therefore was introduced on all cabs. Also, it had been noticed that fighter-bomber pilots tended to work on a train at relatively high altitudes when subjected to antiaircraft fire. All trains, then, would carry a section of light flak. So successful were these measures that a number of divisions actually detrained at railheads only eight to twenty miles behind the front.
There were four main double-track lines running into the Eifel. From 4 September to 10 December all were under the control of the Seventh Army, but on 10 December the two panzer armies moved in to take command of their own sectors. In the north, two lines, Cologne-Duren and BonnEuskirchen, handled the bulk of Sixth Panzer Army traffic. The Ahr River line, fed mainly by the Remagen bridge, supported the Fifth Panzer Army. The Moselle line, following the old Napoleonic "cannon road," handled the Seventh Army trains plus some traffic for the Fifth. Although less rich in rail than