In this period the enemy also considerably developed his activity with high-velocity guns and with aerial bombing, the hutted camps in rear of the trench area, in which the reserve battalions were accommodated, Poperinghe, and the various dumps, all receiving an increasing ration of bombs and high-velocity shells. The value of this form of activity was at once evident, as by a careful employment of high-velocity guns and aircraft, it can be ensured that troops resting behind the line are denied a reasonable night’s sleep, and their efficiency can in this manner be considerably impaired.
On 8th July Divisional headquarters moved to a camp in rear of the trench area, and the G.O.C. 51st Division took over command of the line. While the 152nd and 153rd Brigades were carrying out their tour-of duty in the line, little change in the situation took place, beyond the introduction of mustard-gas by the enemy. This was the most diabolical form of gas produced during the war. Death from its fumes was a prolonged agony ending in suffocation. Post-mortem examinations of its victims revealed the fact that all their organs from the throat to the abdomen were ulcerated throughout. The health of men who survived its effects was often permanently impaired, while externally, particularly in those portions of the body where perspiration is most profuse, the gas raised large blisters, which gradually chafed into open sores. Fortunately, the British mask was found to be absolutely proof against the effects of this gas. It was, however, found to be most persistent in its effects; the liquid contained in the shells became absorbed in the earth and continued vaporising for many hours. As a result, men who were working or living in an area that had been gas-shelled were often infected by the fumes many hours after the shelling had subsided. In some Divisions in the Ypres sector casualties from mustard-gas reached alarming proportions.
After the 154th Brigade had taken over the line, the character of the enemy’s activity changed for the worse. He continued his constant bombardments of the canal bank, and at the same time persistently shelled the forward area, no doubt in the hope that he might knock out any attack that was impending by overwhelming the troops with shell-fire in their assembly trenches.
Some of those bombardments were of great violence, on one occasion 200 trench-mortar bombs being fired into the trenches on one battalion front.
On 28th July a Chinese attack was carried out at 5 A.M. by the Divisional artillery. A Chinese attack consists in passing a moving 18-pounder barrage across the enemy’s trenches exactly as if an attack had begun, except that no infantry take part. The troops in the front line make a considerable noise and hoist dummies on to the fire-step. The German sentries then give the alarm, and as soon as the barrage has passed the garrisons leave their shelters and man their fire-steps. The barrage is then suddenly brought back on to the trenches, and is upon the Germans before they have time to regain their shelters. This is excellent medicine, and after he has been treated to a Chinese attack two or three times, the enemy rather hesitates to man his fire-steps immediately the barrage has passed. Thus, when the day of attack arrives, our infantry, if they can keep close on the heels of the barrage, have an excellent opportunity of “chopping him in cover.” The exposure of the dummies, which have the appearance of troops mounting the parapet, also compels him to disclose the position of his machine-guns, which he normally keeps secret until an infantry attack has begun.
By July 15 each infantry brigade had carried out a tour of duty in the line, so that officers and men had all been given an opportunity of studying the area from which the attack was to be launched. On that date the infantry was therefore all relieved and moved back for training, though the command of the sector still remained in General Harper’s hands.
As regards the area to be attacked, the width of frontage allotted to the Division was slightly over 1400 yards. The enemy’s defences consisted of a front system, including front, support, and reserve line trenches, some 300-500 yards in depth, supported by fortified farms and concrete blockhouses.
About 800 yards in rear of the front system lay a deeply wired line of trenches, supported in front and rear by more fortified farms and blockhouses. This line was known to the Germans as the Stutzpunkt line. To the rear, again, lay further numerous blockhouses and fortified farms. In all cases the blockhouses, as opposed to the farms, which were marked on the map, were not known to exist until they were actually encountered during the operations.
At a distance varying from 1500 to 2000 yards in rear of the Stutzpunkt line lay the Steenbeek, a river which in normal conditions, such as on the morning of the battle, was fordable, but which was liable after rain to rise suddenly and become a serious obstacle, as it did on the afternoon of the battle.