Outbreak of the War (1914)
28 June 1914 — Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, and his wife Sophie were assassinated in Sarajevo by Gavrilo Princip, a Bosnian Serb nationalist linked to the Black Hand.
The assassination triggered the July Crisis. Austria-Hungary, backed by Germany, issued a harsh ultimatum to Serbia. Diplomatic efforts failed. Austria-Hungary declared war on Serbia on 28 July 1914.
The alliance system then activated: Russia mobilized in support of Serbia; Germany declared war on Russia and France; Germany invaded Belgium, bringing Britain into the war on 4 August 1914. Within weeks most of Europe was at war.
Opening Campaigns & the Marne (1914)
Germany launched the Schlieffen Plan, aiming to defeat France quickly by sweeping through Belgium before turning east against Russia. Early German advances reached the outskirts of Paris.
First Battle of the Marne (6–12 September 1914) — French and British forces counter-attacked and halted the German offensive. The German army retreated, ending hopes of a rapid victory in the West.
Both sides then attempted to outflank each other in the “Race to the Sea.” By late 1914 a continuous line of trenches stretched from the Swiss border to the North Sea. Mobile warfare gave way to static trench warfare on the Western Front.
Timeline of Critical Events
Allied attempt to knock the Ottoman Empire out of the war and open a supply route to Russia. Ended in costly failure and evacuation.
German offensive designed to “bleed France white.” Became a symbol of French resistance; enormous casualties on both sides with little territorial change.
Major Anglo-French offensive. First day cost the British over 57,000 casualties. Introduced the tank; ended with limited gains at huge cost.
Tsarist regime collapsed. Bolsheviks seized power in October/November and sought peace, removing Russia from the war.
U.S. declaration of war on Germany after unrestricted submarine warfare and the Zimmermann Telegram. American manpower and resources proved decisive.
Final major German attempt to win before large American forces arrived. Initial gains were significant but the offensive exhausted German reserves.
Allied counter-offensives steadily pushed German forces back. German military and home-front collapse followed.
Fighting ended at 11 a.m. Germany signed an armistice in a railway carriage in the Forest of Compiègne.
Other Decisive Factors
Unrestricted submarine warfare — Germany’s decision to resume unrestricted U-boat attacks in 1917 was a direct cause of American entry into the war.
Treaty of Brest-Litovsk (March 1918) — Russia left the war, freeing large numbers of German troops for the Western Front, but the gains came too late to alter the final outcome.
Naval blockade — The British blockade severely restricted German access to food and raw materials, contributing to hardship on the German home front and eventual collapse.
New technology — Machine guns, artillery, poison gas, tanks, aircraft, and submarines transformed the nature of combat and produced unprecedented casualties.
Outcome & Immediate Aftermath
The Central Powers (Germany, Austria-Hungary, Ottoman Empire, Bulgaria) were defeated. The German, Austro-Hungarian, Russian, and Ottoman empires all collapsed.
The Paris Peace Conference (1919) produced the Treaty of Versailles and related treaties. New states appeared in Central and Eastern Europe. The League of Nations was created in an attempt to prevent future wars.
The human cost was enormous: roughly 9–10 million military dead, millions more wounded, and large civilian losses from fighting, blockade, and the 1918 influenza pandemic.
Most Important Events – Summary
- 28 June 1914 — Assassination of Archduke Franz Ferdinand in Sarajevo.
- July–August 1914 — July Crisis and outbreak of general European war.
- September 1914 — First Battle of the Marne stops the German advance on Paris.
- 1915 — Gallipoli campaign fails; trench deadlock solidifies on the Western Front.
- 1916 — Verdun and the Somme become symbols of industrial-scale attrition.
- 1917 — Russian Revolutions remove Russia from the war; United States enters.
- Spring 1918 — German Spring Offensive fails to achieve decisive victory.
- August–November 1918 — Allied Hundred Days Offensive forces German collapse.
- 11 November 1918 — Armistice ends the fighting.