US Enters World War I

Setting the scene

The United States entered World War I on April 6, 1917, when Congress declared war on Germany. The U.S. had remained neutral since 1914, though it traded extensively with the Allies. Several factors drove entry: Germany's resumption of unrestricted submarine warfare in January 1917, which sank American ships; the Zimmermann Telegram, intercepted by Britain, in which Germany offered Mexico U.S. territory if it joined the war against America; and President Woodrow Wilson's belief that the U.S. must shape the postwar peace.

What happened

Wilson had won reelection in 1916 on the slogan 'He kept us out of war,' but by early 1917, neutrality was untenable. On April 2, Wilson asked Congress for war, declaring 'the world must be made safe for democracy.' The Senate voted 82-6 and the House 373-50 for war. The U.S. mobilized rapidly, instituting the draft in May 1917 and eventually sending 2 million soldiers to France as the American Expeditionary Forces under General John J. Pershing.

Why it still matters

U.S. entry tipped the balance in favor of the Allies. American troops, fresh and numerous, helped stop the German spring offensive in 1918 and spearheaded the Allied counteroffensive. The U.S. also provided crucial financial and material support. American entry transformed the war from a European conflict into a world war and established the U.S. as a global power. Wilson's Fourteen Points shaped peace negotiations, though the U.S. Senate later rejected the Treaty of Versailles and League of Nations, returning to isolationism.

Background

Doughboys tipped manpower on the Western Front.