Archduke Franz Ferdinand, heir to the throne of the Austro-Hungarian Empire, and his wife are assassinated.
Emperor Franz Joseph of Austria-Hungary declares war on Serbia.
The Ottoman Empire signs a secret alliance with Germany agreeing to enter the war once Germany declares war on Russia.
Treaty of Brest-Litovsk is signed between Russia and Germany
Germany declares war on neutral Belgium and invades Belgium and Luxembourg as part of the Schlieffen Plan. As a result, Britain declares war on Germany.
Austria-Hungary declares war on Russia.
The United States declares neutrality in the war.
The German army defeats Russia at the Battle of Tannenberg.
the German invasion of France is halted at the First Battle of Marne.
The Race to the Sea ends when the Germans withdraw at the 1st Battle of Ypres.
Unofficial Christmas truce is declared by German and Allied soldiers in the trenches along the Western Front.
The Germans use poison gas at the 2nd battle of Ypres.
Armenian Genocide begins.
Allies begin a nine-month battle for the Turkish peninsula of Gallipoli.
A German U-boat sinks the Lusitania killing 1,198 civilians, including 128 Americans.
Italy Joins the Allies.
British nurse, Edith Cavell, is executed by the Germans.
The British introduced the tank during the Battle of Somme. The battle resulted in an estimated one million casualties.
Woodrow Wilson is re-elected President of the United States.
The Battle of Verdun was fought resulting in an estimated one million casualties.
The Germans resume unrestricted submarine warfare.
Tsar Nicholas II of Russia abdicates.
The 3rd battle of Ypres, also known as Passchendaele, resulted in minor gains for the Allies and a total of 700,000 casualties.
The Balfour Declaration is presented in London.
President Wilson asks the U.S. Congress for a declaration of war against Germany.
President Wilson outlines his Fourteen Points in a speech before Congress.
British cryptographers deciphered a telegram from German Foreign Minister Arthur Zimmerman to the German Minister of Mexico
Germans on the banks of the Marne near Paris are stopped by American forces at Chateau-Thierry
Kaiser Wilhelm II of Germany abdicates.
At eleven o’clock on this day, war on the Western Front ends as Germany and the Allies sign an Armistice.
Germany and Allies sign the Treaty of Versailles. The U.S. Senate later refuses to ratify it.
The Treaty of Sevres ends the war on the Eastern Front with the Ottoman Empire.
