Every effort was made to give more depth to the new front-line system by pushing forward a line of outposts and by digging a continuous support line, as well as by constructing reserve lines at certain points of greater tactical importance. Switch lines facing south were also sited and dug or improved.
To increase the depth of the defenses, machine-gun detachments were extemporized by borrowing men from the machine-gun battalions, who had then completed their organization on an eight-battery basis. Some fifty extra machine guns were secured from ordnance and other sources, and also a number of extra Lewis guns.
Personnel from the Canadian Light Horse and the Canadian Corps Cyclist Battalion were organized in Lewis and Hotchkiss gun detachments and sent forward to man the defenses in Vimy and Willerval localities, under orders of the Third and Fourth Canadian Divisions.
The machine-gun companies of the Fifth Canadian Division had arrived in France on March 25, 1918, and in view of the extreme urgency of the situation the personnel and armament had been moved by lorries, sent specially by Canadian Corps, from Le Havre to Verdrel, where they were in corps reserve.
Their horse transport having now arrived, these machine-gun companies (Seventeenth, Eighteenth, and Nineteenth) were moved to the Vimy Ridge and allotted definite positions of defense on March 30, 1918.
The front held by the Canadian Corps on April 8, 1918, was approximately 16,000 yards in length. It will be remembered that the Second Canadian Division under the Sixth Corps (Third Army) was holding 6,000 yards of front, making a total of 22,000 yards of front held by Canadian troops.
On April 9, 1918, the Germans attacked on the Lys front between La Bassée and Armentières. Making rapid progress, they crossed the Lys River on the 10th, and on the following days advanced west of Merville-Bailleul. They were well held at Givenchy by the Fifty-fifth Division and their attack made no progress southward.
The Canadian Corps was not involved in this fighting, but it now found itself in a deep salient, following with anxiety the development of the Battle of the Lys.
The Battle of the Lys added a new burden to the already sorely tried British Army, and it was imperative that troops should at once be made available to stop the German advance.
On the 10th, the Canadian front was extended by taking over from the First Corps the line held by the Forty-sixth Division (Lens-St.-Emile-Hill 70 sector). This relief was commenced on April 11, 1918, and completed on the night of the 12th-13th by the Third Canadian Division; concurrently with it, the inter-divisional boundaries were readjusted and the artillery redistributed to meet as well as possible the new conditions.