The front held by the three divisions then in the Canadian Corps had a length of approximately 29,000 yards, and of necessity the line was held very thinly and without much depth.
To deceive the enemy regarding their dispositions and intentions, the Canadians adopted a very aggressive attitude. The artillery constantly harassed the enemy's forward and rear areas and the infantry penetrated his line at many points with strong fighting patrols and bold raiding parties. Gas was also projected on numerous occasions. This activity on the immediate flank of the Lys salient greatly perturbed the enemy, who gave many indications of nervous uncertainty.
The situation was critical, and extensive steps were taken at once to increase the ability of the Canadian Corps to withstand hostile attacks.
The success of the German offensive emphasized the need of greater depth for defensive dispositions, which depend very largely on the stopping power of the machine gun. Unfortunately the number of machine guns with a division was inadequate to give the required depth of defense on a front exceeding 4,000 yards in length. Each Canadian division was now holding a front approximately 10,000 yards in length, and the extemporized machine-gun detachments formed previously, added to the machine-gun companies of the Fifth Canadian Division, were far from sufficient for the task.
General Sir Currie therefore decided to add a third company of four batteries to each battalion of the Canadian Machine-Gun Corps, thus bringing up to ninety-six the number of machine guns in each Canadian division. This entailed an increase in personnel of approximately 50 per cent of the strength of each machine-gun battalion.
These companies were formed provisionally on April 12, 1918, by withdrawing fifty men from each infantry battalion. Of these men a portion was sent to the Machine-Gun Battalion to be combined with the trained personnel, so that each machine-gun crew would include at least four trained gunners. The remainder of the infantry personnel withdrawn as above stated was sent to a special machine-gun depot formed for the purpose, and there underwent an abridged but intensive course of training. Thus an immediate supply of reenforcements was insured. Twenty-three-ton lorries had been borrowed from General Headquarters to supply a modicum of transport to the new units, and on April 13, 1918, some of the new machine-gun batteries were already in the line at critical points.
Sufficient troops were not now available to garrison the local defenses of Vimy Ridge, or to reenforce parts of the front if the enemy was successful in effecting a deep penetration.
Two special brigades were therefore organized:
The Hughes Brigade—Commanded by Lieutenant Colonel H. T. Hughes. Approximate strength, officers, 184; other ranks, 4,050.
McPhail's Brigade—Commanded by Lieutenant Colonel A. McPhail. Approximate strength, officers, 148; other ranks, 4,628.