Day dawned with heavy clouds that promised rain before evening. At 6 o’clock a solitary gun broke the silence. It was the signal, and from just north of the Bapaume road to the hamlet of Gonnelieu in the south, a stupendous barrage crashed from the British line. The whole horizon was aflame, and volcanoes of earth spouted from the German lines. Wakened suddenly from sleep, and dazed with the gun-fire, the enemy sent up star shell after star shell in appeal to his artillery; but, as he strove to man his trenches, out of the fog of dawn came something more terrible than shells—the blunt noses of 350 Tanks tearing and snapping the wire and grinding down the parapets. The instant result was panic. In a few minutes the German outposts fell; presently the main Hindenburg Line followed, and the fighting reached the tunnels of the reserve line. By half-past 10 that also had vanished, and the British infantry, with cavalry close behind, was advancing in open country. General Elles, in his flagship "Hilda," was first in the advance, and it was reported that he did much of his observing with his head thrust through the hatch in the roof, using his feet on the gunner’s ribs to indicate the direction of targets. The "Hilda" flew the flag of the Tank Corps; that flag was several times hit, but not brought down. Comedy was not absent from that wild day. One member of a Tank crew lost his wig as his head emerged from the man-hole, and the official mind was racked for months with the problem whether this came under the head of loss of field equipment, of a limb, or clothing. Nor was heroism wanting on the enemy’s side. The British official dispatch records one instance. "Many of the hits upon our defences at Flesquières were obtained by a German artillery officer who, remaining alone at his battery, served a field-gun single-handed until killed at his gun. The great bravery of this officer aroused the admiration of all ranks." The trial of the Tanks was over. The Battle of Cambrai did not realize to the full the expectations of the British Command. Great successes were won, but our reserves were too scanty to maintain them, and before the battle died away we lost much of the ground we had gained. But of the success of the Tanks there was no question. They stood forth as the most valuable tactical discovery of the campaigns, the weapon which enabled a commander-in-chief to obtain the advantage of surprise and to attack swiftly and secretly on new fronts. It was this weapon which, in the hand of Foch, was destined to break in turn each section of the German defences, and within a year from Cambrai to give the Allies victory. *CHAPTER X.* *THE SOUTH AFRICANS AT MARRIÈRES WOOD.*