World War I was the worst conflict in human history up to that time, with tens of millions of people killed on both sides. The United States stayed neutral until 1917 when it joined the war on behalf of the Allies under President Woodrow Wilson.
On April 6, 1917, over 3 years after World War I began, the United States launched the war on the German Empire. On November 11, 1918, a cease-fire and an armistice were announced. The United States had stayed neutral before entering the war, despite being the main provider to the United Kingdom, France, and the other Allies of World War I.
Beginning in 1917, the United States provided significant efforts in terms of equipment, raw materials, and money. In the summer of 1918, 10,000 American soldiers landed on the Western Front under the command of General of the Armies John Pershing, Commander-in-Chief of the American Expeditionary Force (AEF). During the conflict, the United States sent almost 4 million military members and lost 65,000 men. The war resulted in a massive expansion of the US government in order to coordinate the war effort, as well as a considerable rise in the strength of the US Armed Forces.
After a delayed start in organizing the economy and workforce, the country was ready to participate in the war by spring 1918. The war, led by President Woodrow Wilson, was the culmination of the Progressive Era's efforts to bring change and freedom to the world. The public was overwhelmingly opposed to the United States joining the war.