Triggered by the assassination of Archduke Franz Ferdinand, the heir to the throne of the Austro-Hungarian Empire, World War I began in August 1914 when Germany invaded Belgium and France. Several events led to U.S. intervention: the sinking of the Lusitania, a British passenger liner; unrestricted German submarine warfare; and the Zimmerman note, which revealed a German plot to provoke Mexico to war against the United States. Millions of American men were drafted and Congress created a War Industries Board to coordinate production and a National War Labor Board to unify labor policy. The Treaty of Versailles deprived Germany of territory and forced it to pay reparations. President Wilson agreed to the treaty because it provided for establishment of a League of Nations, but he was unable to persuade the Senate to ratify the treaty.

Consequences

1. Nearly 10 million soldiers died and about 21 million were wounded. U.S. deaths totaled 116,516.

2. Four empires collapsed: the Russian Empire in 1917, the German and the Austro-Hungarian in 1918, and the Ottoman in 1922.

3. Independent republics were formed in Austria, Czechoslovakia, Estonia, Hungary, Latvia, Lithuania, and Turkey.

4. Most Arab lands that had been part of the Ottoman Empire came under the control of Britain and France.

5. The Bolsheviks took power in Russia in 1917 and fascists triumphed in Italy in 1922.

6. Under the peace settlement, Germany was required to pay reparations eventually set at $33 billion; accept responsibility for the war; cede territory to Belgium, Czechoslovakia, Denmark, France, and Poland; give up its overseas colonies; and accept an allied military force on the west bank of the Rhine River for 15 years.