After the stalemate of the fall of 1914, the conflict in France began to slip into a state of almost total war. With millions of men entrenched on opposite sides of a roughly 400km front and the drive for victory unabated, it became a fight to win at any cost. An attritional war is by necessity one without rules and the victor determined by how far they are willing to go to kill off the manpower of the opposing side. While both the Allies and the Entente reached this point eventually, for much of 1915 it was a desperate race for Britain and France to catch up with their enemy. The most frequently seen example of this is the use of poison gas at Ypres in the spring of 1915, which the Allies were quick to adopt, but another terrifying result of the attritional war was the use of tunneling and mining to strike fear into the enemy. The first German mining effort came to light in December 1915, when a section of the line held by the Indian Army near Festubert was blown up at 10:25am, scattering the survivors and leaving a 1 000 yard swathe of trench in German hands. At this point, it was decided by the British High Command that in order to ensure the morale of the men and maintain some kind of control of No Mans Land, they too needed to establish counter mining companies.
Enter John Norton-Griffiths, a Conservative MP and mining magnate; Norton-Griffiths had been campaigning for in the inclusion of tunnellers as a way to break the stalemate on the front since the beginning of the war, and when the explosion happened Festubert he was quick to use it to his advantage. By the spring of 1915, Norton-Griffiths had raised two tunnelling companies of professional miners to be sent to the front to begin countermining operations against the Germans. Canada would follow after an appeal by the British government for its Dominions to form tunneling companies in September 1915, eventually sending a total of three companies recruited and operated by the Canadian Engineers in cooperation with the Royal Engineers. 1st and 3rd Canadian Tunnelling Companies would serve in France at St-Eloi and the Messines Ridge, digging the tunnels that would eventually form the 19 mines that were blown on 7 June 1917, 2nd Canadian Tunnelling Company would be involved in the digging the underground subway and shelter systems used by the British 2nd Army around Ypres.
Captain Oscar Robert Harvey enlisted with the PPCLI in Montreal in April 1915 at the age of 24; a student, Harvey trained with the PPCLI and went to France in July 1915, achieving the rank of corporal before he was transferred to 1st Canadian Tunnelling Company in July of 1916 and promoted to lieutenant. The tunnelling companies had great need of highly specialised, skilled personnel and men enlisted in the infantry who had any mining or engineering experience were often poached to fill the tunnelling companies, much to the chagrin of their former units. Harvey was quickly sent to 2nd Canadian Tunnelling Company where he served for the fall of 1916, digging shelters and transport tunnels in the chalk around Ypres. After several months in the winter and spring of 1917 as a field works instructor, Harvey returned to 2nd Company in July, a month after the explosions at Messines. By 1918, countermining had largely been stopped by both sides, as the cost in time and manpower was deemed too high for the results. Though the tunnelling companies continued to work throughout the war, they slowly shrank again; Harvey himself was transferred out to the regular Canadian Engineers in the summer of 1918, just before the Hundred Days. He was injured in the face on 28 September 1918 during the crossing of the Canal-du-Nord, when the Canadian Engineers were responsible for the construction and installation of the pontoon bridges that would take the Canadian Corps across the canal and deep into the German lines on the other side. Harvey would be demobilised at the rank of captain in 1919 and return to Montreal. Like many tunnellers, Harvey died young at the age of 46, his body worn out after years spent deep beneath the surface of Flanders.
 See Alexander Barrie’s Underground War : The tunnellers of the Great War for a full account of the explosion of the mine at Festubert and the foundation of the tunneling companies by Norton-Griffiths.
 While Harvey’s name does not appear in the records kept by either McGill or the University of Toronto of their graduates who fought in the war, it is likely that he was an engineering student or had some experience of mining to be transferred out of what was shaping up to be a successful wartime career with the PPCLI