Assassination of Archduke Franz Ferdinand and his wife in Sarajevo by Serbian nationalist Gavrilo Princip.
Austria-Hungary's ultimatum to Serbia
Austria-Hungary declares war on Serbia
Russia mobilizes its troops to the south, in clear support of Serbia
Germany declares war on Russia
Germany declares war on France
Germany, under the command of General Von Hindenburg, defeats the Russians at the Battle of Tannenberg. This battle would become a symbol of Germanic pride.
The French army stops the German advance on the Marne, a river in France, thanks to the skill of General Joseph Joffre
Battle of Ypres. The British would stop the German attempt to conquer Belgium in this battle.
Start of the submarine war.
Beginning of the Second Battle of Ypres, Belgium, where Germany used poison gases for the first time.
Treaty of London between Italy and the United Kingdom
Italy declares war on Austria-Hungary
Bulgaria agrees with Germany to enter the war.
Bulgaria declares war on Serbia and obtains Macedonia
Start of the Battle of Verdun, France, also known as the "Hell of Verdun," which claimed 700,000 casualties between German and French forces.
Sykes-Picot Agreement, a secret agreement between France and Great Britain regarding the Middle East.
Start of the Battle of the Somme, Picardy, where tanks were used for the first time in warfare.
Secret Russian-Japanese treaty concerning China.
Italy declares war on Germany.
Charles I of Austria and IV of Hungary ascends to the throne of the Austro-Hungarian Empire after the death of Franz Joseph I of Austria, whose death symbolized the end of 19th-century dominance.
End of the Battle of Verdun, the longest battle of World War I, after ten months.
Peace proposal by U.S. President Woodrow Wilson.
Germany declares unrestricted submarine warfare on merchant ships.
U.S. President Woodrow Wilson proclaims "peace without victory."
Diplomatic relations between Germany and the USA are severed due to naval incidents and submarine warfare.
Abdication of the last Tsar, Nicholas II of Russia, and the beginning of the Provisional Government.
The United States declares war on Germany.
The Battle of Cambrai, France, begins, where the British use tanks and mobile artillery on a massive scale for the first time.
An armistice is signed, ending hostilities on the Eastern Front between Russia, Germany, and Austria-Hungary.
U.S. President Woodrow Wilson proclaims the Fourteen Points, a peace program aimed at addressing the causes of the conflict and preventing future wars.
Treaty of Brest-Litovsk: Russia, under Bolshevik rule, signs peace with Germany, withdrawing from World War I.
Armenia declares its independence from the Russian Empire, establishing the First Republic of Armenia.
Execution of Tsar Nicholas II and his family in Yekaterinburg, marking the end of the Romanov dynasty.