Having received further promotions, Lyall was selected for officer training and sent to the Canadian Officer's Training School in Sussex. After being commissioned in April 1917, Lyall was posted to the 102nd Battalion. As part of the Canadian 4th Division, Lyall's battalion was involved in the Battle of the Canal du Nord on 27 September 1918. Advancing against German forces in Boulon Wood, his platoon was held up by a series of strong points but due to his leadership, these were all overcome. For his actions, he was awarded the Victoria Cross (VC). The VC, instituted in 1856, was the highest award for valour that could be bestowed on a soldier of the British Empire. The citation for his VC read: