If the conflict was protracted Germany would lose the advantage of numbers, for then the greater united manpower of the Allies could be trained for the field, and if the British navy continued to rule the seas those new armies could be supplied and moved at the Allies’ will. Moreover, though Germany could produce most of the necessaries of life and the apparatus of war within her own borders, yet the Allied control of the sea would cut her off from certain vital kinds of war material. The Great War falls therefore into three stages. At the start Germany, with the advantage of surprise and long preparation, embarked on a war of movement in the hope of immediate victory. She failed in this, and the campaign then became a siege in which the Allies sat round her entrenched stronghold. That vast stronghold embraced half of Europe and part of Asia; it could produce most things that it needed, and carry on its normal life. Brilliant sallies were made, which more than once nearly dispersed the besiegers; but, nevertheless, for three and a half years the Teutonic Powers were as the garrison of a beleaguered city. Then came the short, last stage, when the outworks of the fortress crumbled, and the Allies pressed in and forced the garrison to surrender. Germany began the war with Austria as her ally. Within three months she had been joined by Turkey, and by the end of the first year of war Bulgaria mustered on her side. The Allies at the start were France, Britain, Russia, Belgium, Serbia, and Japan; in May 1915 Italy joined them, and in August 1916 Rumania. Before the end Portugal and Greece, among the European Powers, were added; the United States of America joined in April 1917; and in the last year of the war there were altogether eleven Powers in Europe, Asia, and America on their side. The main battles were fought on the Continent of Europe, and the main belligerents, from start to finish, were the European nations. The accession of America, however, was vital for the Allied victory, as it counterbalanced the failure of Russia, which, after the revolution in March 1917, rapidly went to pieces and dropped out of the fighting line. Before telling of any special incidents of the great struggle it is desirable to have before our minds a general bird’s-eye view of the whole war. Germany’s first plan of an immediate conquest was defeated by France and Britain at the First Battle of the Marne in September 1914. She made a second attempt upon the shores of the English Channel, which was foiled before Ypres in November of the same year. After that her policy was to stand on the defensive in the West and to aim at the destruction of Russia. In this, during 1915, she nearly succeeded. The Russian armies were driven out of Poland, but they established their line during the autumn, and Germany’s ambitious strategy had once more failed.