Not until the spring of 1918 did American forces arrive in Europe in large numbers. By then, the world situation had taken a dramatic turn. In November 1917, a communist revolution headed by Vladimir Lenin overthrew the Russian government that had come to power the previous spring. Shortly thereafter, Lenin withdrew Russia from the war and published the secret treaties by which the Allies had agreed to divide up conquered territory after the war—an embarrassment for Wilson, who had promised a just peace.
Partly to assure the country that the war was being fought for a moral cause, Wilson in January 1918 issued the Fourteen Points, the clearest statement of American war aims and of his vision of a new international order. Among the key principles were self-determination for all nations, freedom of the seas, free trade, open diplomacy (an end to secret treaties), the readjustment of colonial claims with colonized people given “equal weight” in deciding their futures, and the creation of a “general association of nations” to preserve the peace. Wilson envisioned this last provision, which led to the establishment after the war of the League of Nations, as a kind of global counterpart to the regulatory commissions Progressives had created at home to maintain social harmony and prevent the powerful from exploiting the weak. Although purely an American program, not endorsed by the other Allies, the Fourteen Points established the agenda for the peace conference that followed the war.
After pears of stalemate on the western front in World War I, the arrival of American troops in 1917 and 1918 shifted the balance of power and made possible the Allied victory.
The United States threw its economic resources and manpower into the war. When American troops finally arrived in Europe, they turned the tide of battle. In the spring of 1918, they helped to repulse a German advance near Paris and by July were participating in a major Allied counteroffensive. In September, in the Meuse-Argonne campaign, more than 1 million American soldiers under General John J. Pershing helped to push back the outnumbered and exhausted German army. With his forces in full retreat, the German kaiser abdicated on November 9. Two days later, Germany sued for peace. Over 100,000 Americans had died, a substantial number, but they were only 1 percent of the 10 million soldiers killed in the Great War.