The first task set for this Corps on August 21 was to capture the general line between Irles in the south and Bihucourt in the north, while the flank of this main attack was to be guarded by a subsidiary advance along the valley of the Ancre, and between Puisieux and Miraumont. The first objective of the {121} main attack was Bucquoy, Ablainzeville, and the important high ground to the immediate east of these villages. The advance commenced in a thick mist, and was undertaken in the case of the main attack by Williams' Thirty-seventh English Division. It was completely successful, and aided by the fire of six heavy and fifteen field brigades of artillery, it swept over its first objectives, the tanks helping materially to break down the opposition. The moral effect of a tank in a fog can be pictured by the least imaginative. Two field-guns and many lighter pieces were taken. The veteran Fifth Division on the right and the Sixty-third Naval Division on the left then passed through the ranks of the Thirty-seventh to enlarge the opening that they had made, carrying the advance on to the limit of the field artillery barrage, and halting at last just west of Achiet-le-Petit. The naval men met with a blaze of machine-gun fire from the edge of Logeast Wood, but they rooted out the nests and occupied the position, though the passage through the tangled brushwood and trees disorganised the units, and progress became slow. The railway line ran right across the front, and this, as usual, had become a formidable and continuous obstacle, which could not be turned. The reserve brigade of the Fifth Division on the right carried Achiet-le-Petit, but could not get over the railway. The Sixty-third was also unable to reach the railway, and found a considerable concentration of Germans opposite to them in the brickworks and cemetery west of Achiet-le-Grand. The tanks had wandered off in the mist, and for the moment the advance had reached its limit. Many of the tanks, as the mist lifted, were hit {122} by the anti-tank guns of the enemy, though some most gallantly crossed the railway line and penetrated the German positions, doing such harm as they could, until they were eventually destroyed.