Canada's Great Shield is a vital warfront of the western hemisphere. We are told how planes opened up the territory to exploration and made possible a new world of mining in the sub-Arctic. Here was developed an aluminum source, vital in war. The strategic significance of Canadian aluminum is pictured against the growth of German armored might. In great plants, Canadian rock ingots are transformed into crank shafts. Tanks and planes and guns are the representatives abroad of Canada's mines.