Having refused to join the League of Nations and ratify the Treaty of Versailles, the United States ratified separate peace treaties with Germany, Austria, and Hungary to officially end its involvement in World War I.
As part of the Second Battle of the Marne, American forces under Gen. John Pershing teamed with the French to earn a key victory at Château-Thierry. The Allied forces executed a surprise early morning counterattack on the Germans, suffering major casualties but gaining important ground.
Allied forces under American Gen. John Pershing began the Saint-Mihiel offensive on September 12. The Allies successfully pushed the Germans out of the Saint-Mihiel salient in France, opening rail communications between Paris and portions of the eastern front and demoralizing German forces.