On December 17th, the Battalion relieved the 6th Battalion Duke of Wellington’s Regt. in the extreme left sector. All knew that this was to be their last tour in the line for the time being and that, on relief, they were to go back for a long period of rest. At night patrols were very active on the Battalion front, on the look-out for indications of the presence of gas cylinders. They reported much hammering in the enemy lines and, on the night of December 18/19th, a great deal of coughing. A raid was contemplated, but that never came off. Much work was in progress, for attempts were being made to put the trenches into better condition for the relieving unit. Working parties from the 6th Division, which was then in Corps Reserve, came up nightly to assist; and the Battalion was also engaged in putting out a great deal of wire on its front. A special artillery “shoot” had been arranged for the early morning of December 18th. This, it was hoped, would not only damage the enemy trenches, but would also destroy any gas cylinders which were in position for an offensive. As the opposing trenches were so near together, the enemy front line could not be bombarded without grave risk to the British themselves. Hence, it was arranged that the Battalion should evacuate its front line at 5-0 a.m. and not reoccupy it until the next night. This was done, but the bombardment did not come off as the morning was too misty for satisfactory observation. So similar arrangements were made for the next day. The night of December 18/19th was comparatively quiet. It was bright and clear, with a gentle breeze blowing from the north-east--in every way ideal weather for an enemy gas discharge. About 5-0 a.m. on the morning of December 19th all front line platoons, except those of A Company, began to withdraw according to plan. Many had actually reached their positions for the day when, at 5-30 a.m., flares suddenly shot up all along the enemy lines. Whether they were red or green is a matter for dispute among those who saw them; but the point is not important. They were evidently a signal for the attack to begin. Immediately, what is described by survivors as a “sizzing” noise was heard, a greenish-white cloud appeared over the enemy parapet and began to drift towards the British lines, and a terrific bombardment with artillery and trench mortars was opened on the Canal, the British communication trenches and reserve positions. Within a few minutes every bridge, except one, was shattered, great damage had been done to the trenches, and every telephone line was broken. And over all drifted that deadly cloud.