During WWI, stalemate on the Western Front produced a new kind of warfare--a network of trenches dug on both sides of the line – and a new breed of soldier fought deep underground using shovels, picks, and explosives. By 1917, the British were staring defeat in the face and focused on a ridge in the Ypres sector of Belgium to breach enemy lines. A network of 19 mines were laid under a ridge by tunnel units – a total of almost one million pounds of explosives. The resulting blast was heard in London.