and less reliable Colt machine gun and an inferior Canadian copy of British webbing equipment that rotted quickly and fell apart in the wet of the trenches. In April 1915, they were introduced to yet another facet of modern war, gas. The Germans employed chlorine gas to create a hole in the French lines adjacent to the Canadian force and poured troops into the gap. The Canadians, operating for the most part in small groups and under local commanders, fired into the flanks of the German advance, forcing it to turn its attention onto the Canadian sector. For three days, Canadian and reinforcing British units fought to contain the penetration with a series of counter-attacks while using handkerchiefs soaked in urine to neutralize effects of the gas. One in every three of the inexperienced but determined Canadians became a casualty. The senior Canadian officers were also inexperienced at first and lacked communications with most of their troops. Notable among these was Arthur Currie, a brigade commander later became the commander of the Canadian Corps and who appointed as his divisional commanders only those who had fought well in this engagement. The battle cost the British Expeditionary Force - BEF (of which the Canadian Corps was a part of) 59,275 men and the Canadian Expeditionary Force over 6000. Battle of the Somme According to historian G. W. L. Nicholson, "The Somme offensive had no great geographical objectives. Its purpose was threefold – to relieve pressure on the French armies at Verdun, to inflict as heavy losses as possible on the German armies, and to aid allies on other fronts by preventing any further transfer of German troops from the west." The Canadian Corps was formed after receiving the 2nd and 3rd and later, 4th divisions. Its first commander was Lieutenant-General Edwin Alderson, who was soon replaced by Lieutenant-General Julian Byng, in time to repulse a German attack at Mont Sorrel in the Ypres sector in June 1916. while much of the BEF was moving toward the Somme. In this engagement, Major-General Malcolm Mercer, commander of the newly formed 3rd Division was killed; he was the most senior Canadian to be killed in the war. The corps did not participate in the battles of the Somme until September, but these began on 1 July after a seven-day bombardment. British losses on the first day amounted to 57,470, which included the casualties of