The Germans' initial offensive on the Western Front in autumn 1914 failed and by the end of the year both sides were bogged down in an unbroken line of trenches from the borders of Switzerland to the coast of the North Sea. For more than three years, the commanders on the Western Front tried to find ways of breaking the stalemate. By the beginning of 1918, the Front had only moved a few miles and millions had been killed. However Russia had been knocked out of the war and the United States had come in on the Allied side. The Germans knew that if they couldn't win the war in the West swiftly in the spring of 1918, they were doomed.
—W A Mckibben