Air attack against the choke points that developed along the main and subsidiary German supply roads seriously impeded both tactical and logistic movement, but much of the over-all delay should be charged to poor German traffic control and road maintenance. Here again the record of achievement by the air is uneven. Movement on the Koblenz-Trier autobahn, a major supply artery for the two southern armies, never was seriously restricted by Allied air attack. As might be expected, the overall effectiveness of air attacks along the roads turned on the configuration of the ground. The 9th Bombardment Division put 136 tons of high explosive on St. Vith, which stood in the open with a wealth of bypass routes around it on relatively level ground, and stopped the German traffic not at all. Even when the RAF dropped 1,140 tons in a carpet bombing attack at St. Vith, the road center was out of commission for only a day. Yet a mere 150 tons put on La Roche over a period of two days stopped all major movement in this sector of the Ardennes road net. La Roche, be it noted, lay at the bottom of a gorge with access only through deep defiles.
The damaging effect of the Allied air attacks against rail lines, bridges, and marshaling yards at and west of the Rhine is quite clear in the history of the Ardennes campaign, but the time sequence between specific rail failures and the resulting impact on German front-line operations is difficult to trace. From 2 December to 2 January the Eighth Air Force, 9th Bombardment Division, and Royal Air Force Bomber Command made daily attacks against selected railway bridges and marshaling yards using an average of 1,800 tons of bombs per day. Yet the day before this bombing campaign began, feeder rail lines in the Eifel had been so crippled by air attack that through movement from the Rhine to the army railheads was no longer possible and supplies were being moved by truck and wagon between the "traffic islands" where rail movement remained in effect. German reports indicate that this transshipment from one mode of transport to another-and back again-cost at least forty-eight hours' delay. By the 26th railway bridges were out on the vital Ahr and Moselle lines, supporting the two southern armies, and the Seventh Army railhead had been pushed back to Wengerohr, near Wittlich. On the 28th the rail center at Koblenz, supporting the German left wing, was put out of operation. And by the close of the year German repair organizations could do no more than attempt to keep some of the railroad island traffic moving.
In retrospect the German effort to keep the railroads operating in support of Army Group B was phenomenal. Five of the eight railroad bridges across the Rhine were put out of service temporarily, generally by bomb damage to the bridge approaches, but all came back into service. Allied air inflicted eighty-five breaks on the Army Group B rail lines west of the Rhine and fifty-four of these were repaired. But in the last week before the Allied ground counteroffensive any hope of maintaining a satisfactory ratio between damage and repair had vanished. Of nine railroad bridges over the Ahr, Moselle, and Nette Rivers, which were designated as high priority targets for air attack, eight were put out of operation on one or more occasions. while for the