World War I

The Allies — Britain, France, Russia (until it left the war), Italy, and, from 1917, the United States — fought the Central Powers led by Germany and Austria-Hungary. Black Americans served in a segregated military; women volunteered on the home front, and a small number served with the American Expeditionary Forces in France.

As a neutral trading nation, the United States supplied the Allies with munitions and loans. German submarines targeted shipping around Britain; the sinking of the British liner Lusitania in May 1915 killed more than a hundred Americans. In 1916 Germany pledged to stop attacking passenger ships without warning (the “Sussex pledge”), and Wilson won reelection on the slogan “He Kept Us Out of War.”

The road to war (January–April 1917). On January 31, 1917, Germany announced it would resume unrestricted submarine warfare, gambling it could defeat Britain before American troops arrived. Wilson broke diplomatic relations. Then British intelligence revealed the Zimmermann Telegram, in which Germany proposed an alliance with Mexico against the United States. On April 2 Wilson asked Congress for a declaration of war; the Senate approved on April 4 and the House on April 6.

Mobilization (1917–1918). Congress passed the Selective Service Act in May 1917. The government took over the railroads, launched shipbuilding programs, sold Liberty Bonds, and created the Committee on Public Information to promote the war. The Espionage and Sedition Acts outlawed criticism of the government and the war, and dissenters were imprisoned.

The Western Front (1918). After Russia left the war, Germany launched a series of massive spring offensives in 1918; all failed by July. From August, American forces joined British and French counteroffensives that pushed the German lines back across France, culminating for the Americans in the Meuse-Argonne Offensive in the fall. Germany’s kaiser abdicated, and the new government agreed to an armistice, effective November 11, 1918.

• Unrestricted submarine warfare and the Zimmermann Telegram (1917): brought the United States into the war.
• The convoy system: American naval escorts helped counter the U-boat threat.
• The failure of Germany’s 1918 spring offensives and the Allied counteroffensives: made German defeat inevitable.

The Allies won. In January 1918 Wilson had proposed Fourteen Points for a lasting peace, including open diplomacy, freedom of the seas, reduced armaments, self-government for subject peoples, and a League of Nations. At the Paris Peace Conference, the Treaty of Versailles created the League but imposed harsh terms on Germany. In the United States, Wilson refused to accept Senate reservations; the Senate rejected the treaty in November 1919 and March 1920, and the United States never joined the League.

More than 115,000 American soldiers died, and between 1918 and 1920 nearly 700,000 Americans died in an influenza pandemic that killed an estimated fifty million people worldwide — more soldiers died of influenza than in combat. Wartime repression gave way to a postwar Red Scare against radicals and immigrants. Labor shortages drew hundreds of thousands of Black Southerners north in the Great Migration, and racial violence erupted in many cities. Women’s war work helped win the Nineteenth Amendment.