While engaged in continually harassing the enemy and also putting the fortress into a proper condition for defence, the Belgian Army was preparing, in the closing days of September, for a fresh and vigorous offensive to be directed chiefly against the left wing of the German containing forces, when it was confronted by a pressing danger which completely altered the aspect of affairs. The Germans, having massed before Antwerp all the huge resources at their disposal, decided to attack the Belgian Army as it lay by breaching the defences of the fortress. On September 29th the first shells from the mammoth guns fell on the forts of Waelhem and Wavre-Sainte-Catherine, doing fearful damage, and from that moment the fate of Antwerp was sealed. The Belgian commander saw this clearly; and one of the things most greatly to his credit will always be that in these tragically momentous hours he was able to keep a stout heart and make the manly decision to abandon a position which he could not hold, in order to save his fighting army and continue the struggle elsewhere without respite or signs of weakening. To cover the operations of evacuating from Antwerp all supplies that could be moved, and to ensure the army's retreat towards the coast, the Belgian troops, though exhausted and half-dead with fatigue, fought steadily for eight days under a fire of unprecedented violence. The order for a general retreat was not given till the night of October 6-7, by which time the limit of resistance had been reached. Only one narrow avenue still lay open--between the Scheldt on the one side and the Dutch frontier and the sea on the other. Protected at first by a flanking guard (a cavalry division and two infantry divisions) and later by a rear-guard of two cavalry divisions, the field army managed by a miracle to reach the Yser, without leaving anything behind in the hands of the enemy during that epic retreat in which the exhausted troops had to cover more than 100 kilometres of congested roads. The Yser line had not been designedly selected. But at the moment it happened to be the nearest line on which the Belgian Army could link up with the Allied forces now gradually advancing northwards along what has been termed "the sea-board route." Prodigies of valour and endurance were still needed to make the continuous front a fact and to shatter the enemy's efforts in the great battle of Flanders.