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Germany declares war on Russia, France and Belgium.
Britain declares war on Germany.
Austria-Hungary declares war on Russia.
France and Britain declare war on Austria-Hungary.
Japan declares war on Germany.
Austria-Hungary declares war on Belgium. The United States declares its neutrality. -
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British and French troops, including Australians and New Zealanders (ANZAC) land on the Gallipoli peninsula in the Ottoman Empire. -
Austro-Hungarian Archduke Franz Ferdinand and his wife, Sophie Chotek, are assassinated by Bosnian Serb nationalist Gavrilo Princip. Austria suspects Serbia is responsible. -
Austria-Hungary declares war on Serbia. -
Germany invades Belgium, but is stopped at the First Battle of the Marne. The Schlieffen Plan fails. -
First Battle of Ypres: Attempting to outflank each other, Allied and German troops were unable to win a decisive victory, leading to the onset of trench warfare. -
Britain and France declare war on the Ottoman Empire. -
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German zeppelin raids on Great Britain begin, bringing the war home to British civilians. -
Germany initiates a policy of unrestricted submarine warfare, whereby all merchant ships, including those of neutral countries, would be subject to attack. -
Second Battle of Ypres: Germans launch the first successful gas attack in history. By the end of the war, both Allied and Central Powers will have used chemical weapons. It ends on May 25, 1915 -
German U-boat torpedoes the Lusitania, a British passenger liner. 128 Americans are killed. -
Italy declares war on Austria-Hungary, entering World War I on the side of the Allies. -
Allied troops move through Mesopotamia to capture Baghdad from the Ottomans. -
A combined force of Austro-Hungarians and Germans (and later Bulgarians) invade Serbia. After weeks of stubborn fighting, the Serbian Army was forced to retreat through Montenegro and Albania. -
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Battle of Verdun: Hoping to “bleed France white,” the German Army launches a major offensive against the symbolic fortress of Verdun. Fighting will not end until December. -
Around 20,000 French women and girls are deported from industrial cities like Lille to perform forced agricultural work in other parts of occupied France. -
Great Britain and France secretly sign the Sykes-Picot Agreement. Assuming they will defeat the Ottoman Empire, they divide the Middle East. France claims Syria and Lebanon. Britain claims Jordan, Iraq, the Gulf states and the Palestine Mandate. -
Battle of Jutland: In the largest naval battle of the war, Britain’s Royal Navy Grand Fleet and the German Navy’s High Seas Fleet fought to a draw, though both sides claimed victory. -
Arab nationalists revolt against Ottoman rule in the “Great Arab Rising.” -
Battle of the Somme: After a seven-day artillery bombardment, Allied troops launch an offensive meant to divert German troops from Verdun. The British suffered around 50,000 casualties on the first day and fighting continued until November. -
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After Germany resumes its campaign of unrestricted submarine warfare, the U.S. severs diplomatic relations with Germany. -
British intelligence intercepts the Zimmermann Telegram, a secret communication from Germany proposing an alliance with Mexico should the United States enter World War I. -
Germany sinks the SS Aztec, a U.S. cargo ship bound for France. -
U.S. President Woodrow Wilson delivers a war message to Congress, famously stating that “the world must be made safe for democracy.” -
Following passage of the war resolution by the Senate and House, the United States is officially at war with the German Empire. -
Having traveled on a sealed train from Switzerland, Vladimir Lenin returns to Petrograd (St. Petersburg) after a decade of exile to personally lead the Russian Revolution. -
The U.S. Congress authorizes the Selective Service Act, initiating the first military draft since the Civil War. -
General John J. Pershing selected as commander of the American Expeditionary Forces. -
Congress passes the Espionage Act, making it a crime for any person to convey information intended to interfere with the prosecution of the war effort or to promote the success of the country’s enemies. -
Third Battle of Ypres (Passchendaele): Allied troops, largely those from the British Empire, launch an attack to seize key ridges near Ypres. They achieve victory, but only after months of fighting in horrific conditions and sustaining heavy casualties. -
Britain issues the Balfour Declaration, a statement of support for the establishment of a Jewish nation in Palestine. -
Vladimir Lenin and the Bolsheviks assume complete control over the new Soviet Russian state. -
French munitions ship collides with a Belgian relief ship resulting in 11,000 casualties. -
The British capture Jerusalem from the Ottomans. -
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U.S. President Woodrow Wilson outlines his Fourteen Points for peace. -
Russia and Germany sign the Treaty of Brest-Litovsk, officially removing Russia from World War I. -
Camp Funston at Fort Riley, Kansas makes the first report of influenza. The disease spreads overseas to the Western Front. Over the next year this “Spanish Influenza" kills 20 million worldwide. -
Battle of Cantigny: In its first major battle of World War I, American troops captured the town of Cantigny, depriving the Germans of an important observation point. -
Bolsheviks murder the former czar of Russia, Nicholas II, and his family. -
Aisne-Marne Offensive: Marks a major turning point in the fighting on the Western Front. Two days after its conclusion, the British attack at Amiens is called the “Black Day of the German Army.” -
Battle of Saint-Mihiel: First major offensive operation by General John J. Pershing’s American Expeditionary Forces. It ended 3 days later. -
Meuse-Argonne Offensive: After a short artillery bombardment, American and French troops advance toward German positions in the Argonne Forest and along the Meuse River. The largest offensive in U.S. history, it played a major role in bringing about an end to the war. -
Battle of Vittorio Veneto: Austro-Hungarian forces are severely defeated by the Italian Army, ending the war on the Italian Front and ushering in the final dissolution of the Austro-Hungarian Empire. -
German Kaiser Wilhelm II abdicates and flees to Holland. German Republic (later the Weimar Republic) proclaimed. -
Having been given 72 hours to agree to Allied demands, Germany signs the armistice. Supreme Allied Commander Marshal Ferdinand Foch orders that all hostilities on the Western Front cease at 11 a.m. Paris time. -
Allied troops move into Germany and begin occupation. -
Yugoslavia, a kingdom of Serbs, Croats and Slovenes is proclaimed an independent state. -
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At the Paris Peace Conference, Allied nations propose constitution for the League of Nations to promote international cooperation. -
Germany is forced to sign the Treaty of Versailles. Germany cedes Alsace-Lorraine to France, recognizes Belgian sovereignty, disarms and agrees to pay war reparations. U.S. Senate refuses to ratify the Treaty of Versailles, thus preventing the country from joining the League of Nations. -
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The Treaty of Sevres officially ends the war between the Allies and the Ottoman Empire and marks the beginning of the latter’s partitioning. Only the territory that becomes Turkey is independent of British and French control.