At 3 P.M. on the 21st the 9th Royal Scots carried out an operation with a view to extending our hold on this road farther southwards. This attack was at first successful, but subsequently a local counter-attack on the right restored the situation for the enemy. The net result was, however, that one additional post was established 150 yards in advance of the sunken road. Meanwhile, on the left, where the trenches were well clear of the river, work was carried on in digging new assembly trenches. As a preparatory measure attempts were made to harass the enemy with discharges of gas. The difficulty of bringing up the necessary apparatus was great owing to the poor communications, and the plan met with little success. On one occasion a sergeant in charge of a train of mules loaded with gas, which came under heavy shell-fire on the railway embankment, noticed that his men were showing some signs of nervousness as the shell splinters came amongst the cylinders. He therefore encouraged them by shouting out in a stentorian voice, "Great God A-michty, ye canna a' be killed." Apparently his words of encouragement comforted the party, as it continued on its way without any further misgivings. The plan of action for the operation was that the 17th Division should attack south of the Scarpe, and that the 37th Division should continue the attack to the left of the 51st. Objectives were selected as follows:-- The first objective, known as the Black line, was a line running west of the Roeux-Gavrelle Road, excluding the buildings of the chemical works and the village of Roeux. The second objective, the Blue line, included the western half of the village of Roeux, the chemical works, and the Roeux-Gavrelle Road. The third objective, the Brown line, took the line of the road running due north from the eastern end of Roeux, and included all the remaining trenches of the German front system. The fourth objective, the Red line, included Hausa, and Delbar Woods and Plouvain Station. The final objective, the Pink line, included Plouvain. The 154th Brigade was detailed to attack on the right, the 153rd Brigade on the left. The 154th Brigade had a particularly difficult operation to perform, as the frontage available for the assembly of their troops was considerably narrower than the frontage to be attacked. The attacking lines had therefore to expand laterally as the advance progressed, so as to cover the whole of the frontage allotted to them. The number of guns available for the barrage appeared inadequate for an operation of this nature. It was anticipated that, as the enemy was practically without dug-outs to which he could be driven by the approaching barrage, he would have no other alternative but to remain in his shell-holes and fight.