World War I
The 'Great War' that killed 20 million people, destroyed four empires, and reshaped the world between 1914 and 1918.
Assassination of Archduke Franz Ferdinand
A Bosnian Serb nationalist kills the heir to the Austro-Hungarian throne in Sarajevo, triggering the alliance system that will drag Europe into war.
War Engulfs Europe
Within six weeks, the alliance system draws all major European powers into war — Germany and Austria-Hungary against Britain, France, and Russia.
Battle of the Marne Halts German Advance
France stops Germany's Schlieffen Plan at the Marne, beginning the trench warfare stalemate that will define the Western Front.
First Large-Scale Poison Gas Attack at Ypres
Germany deploys chlorine gas against Allied troops — a horrifying new weapon that epitomizes the industrialization of killing.
Armenian Genocide
The Ottoman government systematically murders an estimated 1–1.5 million Armenian civilians — one of the 20th century's first genocides.
Battle of the Somme
The British suffer 57,000 casualties on the first day alone. Over five months, more than a million men are killed or wounded for minimal territorial gain.
February Revolution in Russia
War-weariness, food shortages, and military disaster topple Tsar Nicholas II — ending over 300 years of Romanov rule.
United States Enters the War
Provoked by unrestricted submarine warfare and the Zimmermann Telegram, America's entry provides the manpower that will tip the balance.
Bolshevik Revolution in Russia
Lenin and the Bolsheviks seize power in Petrograd, establishing the world's first communist state and withdrawing Russia from the war.
Armistice Ends World War I
Germany signs the armistice at 11 AM on the 11th day of the 11th month. The war has killed approximately 20 million people.