On June, 28, 1914, Archduke Francis Ferdinand of Austria was assassinated by a Serbian nationalist. Nationalist fervor had been brewing in Europe, and Serbia was then under the dominion of the aging Austro-Hungarian Empire. The assassination was the spark; the accumulated tinder was composed of imperial and economic rivalries among major European powers. These rivalries had produced an arms race and a tangle of military and economic alliances.
Austria declared war on Serbia on July 28, 1914; then Germany declared war on Russia and invaded Belgium; as a result of the invasion England declared war on Germany. The war of the Central Powers (Austria-Hungry, Germany, Bulgaria, Turkey) against the Allies (Great Britain and its allied nations, France, Russia, Serbia, Greece, Italy) had begun. Public antiwar sentiment kept the United States out of the conflict until April 6, 1917, when the United States joined the Allies, who had been receiving U.S. support. President Woodrow Wilson had won reelection in 1916 with the aid of the slogan “He Kept Us out of War,” but the prowar position took precedence as a result of Germany’s sinking U.S. ships and of the publication of an intercepted telegram from Germany to Mexico suggesting that Mexico ally itself with Germany. The war of attrition ended with the collapse of the Central Powers’ war machine in 1918.