The later stages of the attack were, however, planned to pass over the ridge and reach the plains beyond it. The wire to be encountered in this phase of the attack was, therefore, on the reverse slope of the Vimy Ridge, and could only be seen from the air.
Unfortunately, at this period the German air service established a marked superiority over our reconnaissance machines. In a single period of twenty-four hours, three R.E. 8’s (reconnaissance aeroplanes) were crashed within full view of a single brigade headquarters, one of them being hunted right down to the ground, where it overturned, with both its occupants wounded.
At this period the policy of the Higher Command was to wait till a new type of aeroplane was completed, and then definitely and suddenly to take command of the air. This superiority, of which the Germans were successfully deprived, as planned, on the opening of the offensive, was due to the arrival in this part of the line of the “circus”—that is, the squadron commanded by Baron von Richthofen—which included the picked fighting pilots of the German air service. The aeroplanes used by this squadron were painted red, with yellow or pink bellies, and gave to laymen, at any rate, an impression of amazing efficiency.
In consequence of this temporary superiority in the air, the wire-cutting on the reverse slopes of the ridge could seldom be successfully carried out. It was, however, at this period that the now famous 106 or instantaneous fuze arrived in the country. This fuze burst its shell instantaneously when the fuze-cap touched the ground. As a result, the explosion occurred before the shell had time to bury itself in the earth, and its full force was therefore felt above ground. The effect of this shell on wire was devastating, and an accurate shot would blow a gap clean through an ordinary entanglement. So much was the energy of this shell spent on the surface of the earth, that even heavy howitzer shells left craters little bigger than wash-hand basins.
The plan was that no action should be taken which was likely to warn the enemy of an impending attack until as late as possible. Therefore in February and the early part of March wire-cutting was only carried out in conjunction with raids.
As regards the preparation of the troops for the attack, much time had already been spent in teaching the lessons gained at the battle of Beaumont Hamel to the new drafts which had since arrived. General Harper had been continuously developing his theories on the application of tactical principles to the conditions of modern warfare. Possessed of great gifts of imagination and powers of deduction, he was in this respect always in advance of his time. He therefore spared no pains to train the Division in the practice of his theories. He achieved this object to a certain extent by lectures to officers and men, but more particularly by informal discussions. He regularly visited units in the line and out, and seldom left without having discussed some tactical principle, explained his views on it, and impressed all with their soundness. What the General thought to-day the Division thought and practised the following week.
The main principles on which General Harper based the training of his units and planned his attacks at this time may be summarised as follows:—
1. That the objective of all offensive operations must be to envelop the enemy—i.e., hold him in front and attack him in flank.
2. That the fullest use must at all times be made of mechanical weapons—i.e., guns, machine-guns, trench-mortars, &c. The minimum use of infantry; to rely for success on the weight of infantry, either in attack or defence, was to ensure unnecessary casualties.
3. That troops must always be in depth; they must neither attack nor defend in one or two dense lines of men, but in a succession of well-extended lines.