Had the effort succeeded both parts of the Allies' line must have been forced into retreat and their communications severed. This success must have changed the entire aspect of the western operations. For the Allies it would have been a disaster of the first magnitude. If in this effort the Germans sacrificed their best troops, it affords only another illustration of the statement that they do not make such sacrifices without what they consider good cause. But the effort failed, and the German Headquarters Staff, at any rate, must have realised that the failure and the cost of it had imperilled the whole position of their armies in France. Matters of this kind have not to be judged only by ground lost or won. The success or failure to achieve objectives is the true test. Meanwhile heavy forces of the Allies had been massed against the German right flank. The next effort of the Germans consequently was to push back those forces. They met the outflanking movement in the way such movements can best be met--by trying to outflank the outflankers. At this time the Allied forces on the flank extended from near Noyon on the Oise northward to the Somme. The Germans promptly pushed westward in force north of the Somme and across the outside edge of the Allied line to the town of Albert and the heights commanding it. With notable promptitude, however, the Allied line was extended across the Somme to the north, and by the west of Arras, and the German movement was held. Gradually, after days of obstinate fighting, the enemy were battled out of Albert and then out of Arras; and the Allied outflanking line was stretched up to Bethune and La Bassée. Night and day, day and night, by railway, by motor-omnibus, on motor-cars,[33] French troops during three whole weeks were rushed up from the south and west of France. This movement towards the fighting line had begun with the pursuit after the Battle of the Marne. It never ceased. First the army of General de Castlenau appeared on the front. Next came the army of General de Maudhuy. Territorials and marines from the fleet were hurried into the service; divisions of cavalry spaced out the line, and defended communications. In Germany as in France no effort was spared. The issue was momentous. During these first weeks of October the German Government put forth its supreme effort to stem and to turn the adverse tide of war. Hitherto they had found their measures baffled. Two new and powerful French armies had fastened on to the flank of their position. Their own forces had come up just too late. The peril was menacing and it was growing. They redoubled their energies. Their decision was another supreme effort to outflank the outflankers. With fresh masses of Reservists, sent westward at all possible speed, they pushed behind a heavy screen of cavalry across the Aa and across the Lys at Estaires and threatened the rear of the French troops holding Bethune.