Whose the credit for the conception of the surprise tank assault, whether General Tudor's or General Ellis's, or another's, it is not here pertinent to speculate. The germ of the idea was inherent in the tank itself, and must have been present, vaguely or clearly, in the minds of all who contributed to its design and organization. Here, at any rate, had been found an ideal testing-ground for the scheme, good ground, obstacles which it would have, at that date, been madness to attack in the conventional manner, the prospect of inflicting upon the enemy a swift and signal defeat. Moreover, a blow that would prevent the massing of more German divisions on the Italian front, where every German division put new life and dash into at least two Austrian, was urgently needed. The striking of the blow was entrusted to General Byng's Third Army. The plan was simple. The tanks were to roll out gaps in the wire of the Hindenburg System, through which the infantry columns could push. The aim was to overcome the enemy holding the line between the Canal du Nord and the Canal de l'Escaut, which runs parallel with it at a distance of from six to eight miles further east; to secure possession of the area bounded by these Canals on east and west, and by the marshes of the Sensée River to the north; and, as a consequence, to clear the whole area west of the Canal du Nord of hostile forces. It must be remembered that the German line, running north from Havrincourt to Mœuvres, there turned west by north. Had the British, pressing northward, reached Oisy-le-Verger and the banks of the Sensée River, they would have been ten miles behind the German front line at that latitude. A precipitate retreat would have been certain, and a very large haul, if not of prisoners, at least of material, almost equally so. Even if the advance to the north accomplished no more than the consolidation of the high ground round Bourlon Wood, the Germans would have to abandon the Drocourt-Quéant Switch, a very strong position. The battle was to have three stages: the first, a surprise infantry attack assisted by tanks and an unregistered artillery barrage to capture the crossings of the Canal de l'Escaut at Masnières and Marcoing, and a German trench east of them known as the Masnières-Beaurevoir Line; the second, the advance of the Cavalry Corps to isolate the city of Cambrai, and seize the crossings of the Sensée River, while the troops of the IV. Corps captured Bourlon Wood; and the third, the clearance of the area and of Cambrai itself. The attack was to be carried out by the III. Corps on the right and the IV. Corps on the left, with the V. Corps in reserve. The right flank of the attack lay upon the great spur, crowned by the Bois Lateau and the hamlet of Le Pave, running from Gonnelieu to the Canal de l'Escaut at Crèvecœur; the left roughly upon the Canal du Nord. There was to be a subsidiary attack to the north upon the Hindenburg Line at Bullecourt. If one were to search