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Assassination of Archduke Franz Ferdinand
The heir to the Austro-Hungarian throne, Archduke Franz Ferdinand and his wife Sophie were killed in Sarajevo by a Serbian nationalist named Gavrilo Princip. Princip was a member of a secret society called the Black Hand that was bent on freeing the Balkan states from Austro-Hungarian rule. -
Austria-Hungary declared war on Serbia
Unsatisfied with Serbia's response to Austria's punishing ultimatum, Austria-Hungary declared war on Serbia. -
Russia mobilizes troops
Russia, as Serbia's protector and ally, began mobilizing its troops in preparation for war. -
Germany declared war on Russia
After a furious exchange of telegrams between Germany's kaiser Wilhelm and Russia's czar Nicholas (both cousins), Russia refused to stop mobilizing their troops and Germany declared war on Russia. -
US President Woodrow Wilson declared the US a neutral country
The US President Woodrow Wilson officially proclaimed the US a neutral country to protect US overseas investments. -
Warning from the German Embassy
The German embassy issued a warning urging overseas passengers traveling on British ships that there was a war taking place and British ships risked attack by the German navy. -
The sinking of the Lusitania
A German U-boat sank a British passenger liner off the coast of Ireland. 128 American citizens died. Germany argued there were munitions aboard and President Wilson called for an immediate end to unrestricted submarine warfare. -
Battle of Verdun
The Germans launched a major offensive against the Allied forces in France. The battle, which ended in December 1916, resulted in nearly 1 million casualties. The French were able to hold their position, but at a massive loss in manpower. -
The sinking of the Sussex
A German U-boat torpedoed a French passenger ship, the Sussex. Two Americans were aboard (not killed) and the US threatened to cut diplomatic ties with Germany. -
The Sussex pledge
After protests by the American government, Germany promised to end the tactic of unrestricted submarine warfare -
Battle of the Somme
The British military supported by other Allies launched an offensive near the Somme River in France to draw Central Power forces away from Verdun. Brutal fighting led to an estimated 1 million casualties on both sides. The British gained a mere 6 miles of territory and failed to reach their objective. -
Explosion at Black Tom munitions depot
German spies were accused of setting fires and detonating large explosions to sabotage the Black Tom depot and prevent the US from delivering the arms to the Allied Powers. -
Germany resumed unrestricted submarine warfare
Germany, in an effort to further inflict damage on the Allied Powers resumed their naval operations of unrestricted submarine warfare. -
US broke off relations with Germany
The United States in response to Germany's resumption of unrestricted submarine warfare breaks off diplomatic relations with Germany and draws closer to World War I. -
Zimmermann Telegram
The British intercepted a coded telegram urging Mexico to wage war against the United States in exchange for a return of the American Southwest the US had previously taken. The American and Mexican governments do not take the telegram very seriously, but it is a major propaganda victory for the Allies. -
Germany sinks American ships
Between March 16 and 18, Germany sank the City of Memphis, the Illinois, and the Vigilancia. By March 20, President Wilson's Cabinet had voted unanimously for war with Germany. -
President Wilson signs war resolution
Following Germany's resumption of unrestricted submarine warfare, Wilson gained approval for a declaration of war by Congress and signed the document, officially entering the US into World War I. -
Russia withdrew from the war
Following the Bolshevik revolution, Russia led by Vladimir Lenin signed the Treaty of Brest-Litovsk allowing for Russia to withdraw from the war. Russia's withdrawal put additional pressure on the French and British and drove the US closer to the Allies. -
Armistice signed ending World War I
An armistice, or cease-fire is signed bringing an end to hostilities on the 11th hour of the 11th day of the 11th month. The two sides will now have to negotiate a peace arrangement. -
Treaty of Versailles signed
The European powers signed the Treaty of Versailles, officially ending the war between them. The US never signed the treaty and arranged separate peace agreements with the warring nations.
