For this attack the Divisional artillery was reinforced by the two brigades of the 11th Divisional artillery and by two army brigades, the 77th and the 282nd. These six brigades were divided into two groups of three brigades each, one group under the command of Lieut.-Colonel L. M. Dyson, D.S.O., covering the 152nd Brigade; the other, under the command of Lieut.-Colonel M. M. Duncan, C.M.G., covering the 153rd. A brigade of artillery covered each of the four battalion frontages, while the remaining brigade in each group covered the whole brigade front. This plan gave one 18-pounder gun to every twelve and a half yards of the front. One hundred and twelve machine-guns were available for this attack, as a fourth machine-gun company, the 232nd, had now joined the Division, and forty-eight guns from the 11th Division were also placed at the disposal of the 51st. Of these, sixty-four fired three successive barrages, covering the ground in front of the Blue, Black, and Green lines. Sixteen were placed under the orders of the Brigadiers for purposes of consolidation, and thirty-two were kept in reserve. As the attack was launched 206 drums of burning oil were projected from mortars on the enemy's support and reserve lines, while to discourage the enemy further 150 shells filled with thermite were thrown at Fort Caledonia in the German reserve line three minutes after zero. There seemed to be rather a mediæval touch about the employment of drums of burning oil; but according to the statements of prisoners who experienced it, it appeared to have been as effective as ever. One squadron of the 1st King Edward's Horse and eight fighting tanks, with one supply tank, were also placed at the disposal of the Divisional commander. The artillery had begun the cutting of the enemy wire on the 16th July, and for a fortnight were firing with great intensity, their average daily expenditure being 3500 rounds by the 18-pounders, 1000 rounds by the 4·5 howitzers, and 400 rounds by the 2-inch trench-mortars. Naturally this great activity on the part of the gunners drew considerable retaliation from the enemy; nevertheless, they carried out their task with a precision that was little short of amazing when the fact is taken into account that they had to work entirely by aerial observation.