America enters World War I
Nine days later, notice was received from the German government that unrestricted submarine warfare would be resumed. In the United States this announcement was commonly considered to have made war inevitable. On April 2, 1917, after five American vessels had been sunk, Wilson appeared before Congress to ask for a declaration of war. Immediately the American government set about the task of mobilizing its military resources, its industry, labor and agriculture. Soon one massive convoy after another was sailing from American ports and, by October 1918, there was an American army of over 1,750,000 soldiers in France.
The first of the American forces to make itself felt was the navy, which performed a crucial task in helping the British break the submarine blockade; then in the summer of 1918, during a long-awaited German offensive, fresh American troops played a decisive part on land. In November, an American army of over a million took an important part in the vast Meuse-Argonne offensive which cracked the vaunted Hindenburg line.
As a wartime leader Wilson himself was immensely effective. One of his greatest contributions to an early conclusion of the war was his eloquent definition of the war aims of the Allied powers. From the beginning he insisted that the struggle was not being waged against the German people but against their autocratic government. In January 1918, he submitted to the Senate his famous Fourteen Points as the basis for a just peace. He called for the abandonment of secret international understandings, a guarantee of freedom of the seas, the removal of economic barriers between nations, reduction of national armaments, and an adjustment of colonial claims with due regard to the interests of the inhabitants affected. Other points, more specific in character, were designed to assure European nationalities self-rule and unhampered economic development. In his fourteenth point, Wilson formulated the keystone of his arch of peace-the formation of an association of nations to afford "mutual guarantees of political independence and territorial integrity to great and small states alike."