On February 3, 1917, the United States of America ranged themselves on the side of the Allies, but their eventually powerful effort could not make itself seriously felt before the summer of 1918. In March 1918, four American divisions were in France, and a million more men were expected by the following Autumn, but the Germans were convinced that they would have the Allies beaten before then. The moral strength of the opposing forces constituted one of the most important factors of victory. During 1917, after the Allies' Spring Offensives, a wave of lassitude had lowered the fighting spirit of certain units of the French Army. However, the _morale_ of the French Army had fully regained its former high level, when the great German offensive of March 1918 was launched. The British Army had in the meantime perfected its training, and acquired, in addition to experience, splendid fighting qualities. The Germans, badly shaken in 1916 by their failure at Verdun and by the Allies' Offensive on the Somme, had, in consequence of Russia's collapse, recovered all their former arrogant confidence and pride. But the Allies' blockade, despite Germany's ruthless submarine warfare, tightened, and each day the menace of famine increased. Triumphal announcements of victory, and promises of an early German peace appeared periodically in their press, yet still the war dragged on. Something had to be done to end it all, whatever the cost, and so the "Peace Offensive" was decided on. Although inferior in numbers and equipment, the Allies had acquired moral superiority. [Illustration: DRIVEN FROM HOME BY THE GERMAN PUSH. (_Photo Imperial War Museum_).] The German Strategy and Tactics. In all the previous offensives, especially that of the Somme in 1916, the artillery had been used, prior to the attack, to destroy the adversary's defences. The great number of fortified works and their ever increasing strength necessitated a proportionately longer and more intense artillery preparation. Thus warned, the enemy were able to make dispositions to counteract the effects of the attack, and to bring up reinforcements. Moreover, the tremendous pounding of the ground greatly hampered the advance of the storming troops, who were hindered at every step by the enormous shell-holes and craters. Breaking away from past errors, and adopting and perfecting the methods inaugurated the previous year before Riga, the German High Command attacked by surprise, in March 1918, thereby securing a crushing numerical superiority. The Allies were thrown into confusion, and all attempts at resistance were unavailing, until the arrival of the reserves. During this period of complete demoralisation, the enemy were able to exploit their initial success to the full.