The Unit continued to operate at Aire until January, 1916, when it was transferred to Bailleul and opened up in a very fine pavilion of the Asylum for the Insane. This splendid building was subsequently destroyed by German shell fire and bombs. The Unit saw much strenuous work here, and had its first experience with gassed cases. Sixty of these out of eight hundred died within the first twenty-four hours after being brought in. Major Edward Archibald, of No. 3 (McGill) Canadian General Hospital, was attached to the Unit as a surgical specialist, and Major W. A. McLean, of Glace Bay, N.S., was transferred from No. 1 Canadian General Hospital as his assistant, and afterwards succeeded Major Archibald. Major McLean was killed during the summer of 1917 while at work in a C.C.S. in the northern sector of the British line. He was considered one of the most brilliant surgeons in the British Army. In June, 1916, Colonel Ford was appointed Deputy Assistant Director of Medical Services of the Canadian Corps and Lieut.-Col. T. W. H. Young succeeded to the command. Later Colonel Young was succeeded by Major C. H. Dickson, who was promoted to the rank of Lieut.-Colonel. There was a great deal of activity on the Arras Front in the early spring of 1917, and preparations were being made for the drive for Vimy Ridge. At this time the Unit was transferred to Aubigny, behind Arras. Under the energetic administration of Lieut.-Colonel Dickson this Unit was very much increased in strength and did valuable work during the Battle of Vimy Ridge and throughout the operations on the Arras Front. In the summer of 1917 the Unit was again moved to a position near Nieuport and arrived just as the Germans had broken through and made a nasty salient in the British line. Amidst this confusion, uncertainty and fierce fighting, the Commanding Officer, Colonel Dickson, quickly located his Unit and did such splendid work in the evacuation of the wounded that he was mentioned in despatches and awarded the D.S.O. The Unit remained at Nieuport for a few weeks only when the position became untenable for hospital purposes, owing to almost constant shelling and nightly bombing. Lieut.-Colonel Dickson was called to London for Staff duty, the command was taken over by Lieut.-Colonel A. G. H. Bennett, O.B.E., and the Unit was transferred again to the Arras-Vimy Front. During those anxious days of the early spring and summer of 1918, while the Germans battered themselves hopelessly against the impenetrable wall of steel erected by the Canadians along the Arras Front this Unit did fine work in caring for and clearing the seriously sick and wounded and also got many casualties from that memorable drive of the Germans against the 5th British Army in March, 1918, as all the Ambulance and C.C.S. Units in that area were quickly put out of commission.