Key takeaways
- Wikipedia dates World War I from 28 July 1914, when Austria-Hungary declared war on Serbia, to the Armistice of 11 November 1918.
- Germany was at war with Russia from 1 August, declared war on France on 3 August 1914, invaded Belgium on 4 August, and Britain entered the war at midnight.
- The first day of the Somme, 1 July 1916, cost the British Army 57,500 casualties including 19,200 dead, its bloodiest single day.
- The US declared war on 6 April 1917; the National Archives says the Zimmermann Telegram helped convince Congress.
- Wikipedia gives a death toll of 15 to 22 million; the formal state of war with Germany ended with the Treaty of Versailles on 28 June 1919.
World War I ran from 28 July 1914, when Austria-Hungary declared war on Serbia, to the Armistice of 11 November 1918 — 1,567 days by the calendar. Wikipedia puts the dead at 15 to 22 million, including those killed in war crimes and genocides. This page is a year-by-year timeline of what happened in between. Why it began is a separate question, covered in what actually started the First World War; here the aim is simply to get the sequence right.
1914: from an assassination to a trench line
| Date | Event |
|---|---|
| 28 June | Gavrilo Princip, a Bosnian Serb, assassinates Archduke Franz Ferdinand in Sarajevo |
| 28 July | Austria-Hungary declares war on Serbia; Russia then mobilises in Serbia's defence |
| 1 August | Germany's ultimatum to Russia expires; the two are at war |
| 2–3 August | Germany occupies Luxembourg and declares war on France, demanding passage through Belgium |
| 4 August | Germany invades Belgium; Britain's ultimatum expires at midnight and Britain is at war |
| September | The German advance on France is halted at the First Battle of the Marne |
| November | The Ottoman Empire joins the Central Powers |
Wikipedia explains that Germany's plan was to defeat France quickly and then turn on Russia. After the Marne, both sides tried to outflank each other in the "Race to the Sea," and by the end of 1914 the Western Front had set into a near-continuous line of trenches from the English Channel to Switzerland.
1915: new fronts, no breakthrough
The Allies looked elsewhere. Wikipedia records the failed Gallipoli campaign, in which the Ottoman Empire repelled British, French and ANZAC forces, and a campaign in Mesopotamia begun in 1914. Under the secret Treaty of London of April 1915, Italy joined the Allies and declared war on Austria-Hungary on 23 May, fighting a mountain war along the Isonzo. Wikipedia notes the German army was the first to deploy chemical weapons successfully, with chlorine at the Second Battle of Ypres in April–May 1915. At sea, the sinking of the liner Lusitania in 1915 led Germany to promise not to target passenger ships. The Ottoman deportations and killings of Armenians that began in 1915 are covered in the Armenian genocide explained.
1916: the year of attrition
Germany attacked at Verdun in February 1916, and the battle lasted until December; Wikipedia gives anywhere from 700,000 to 975,000 casualties between the two sides. The Anglo-French Somme offensive ran from July to November.
The Somme's first day shows why casualty figures need reading carefully. On 1 July 1916 the British Army suffered 57,500 casualties, including 19,200 dead. The dead are counted inside the casualty figure, so they were 19,200 ÷ 57,500 ≈ 33% of it — about one in three; the other 38,300 were casualties who were not recorded among the dead. Across the whole offensive Wikipedia estimates 420,000 British, 200,000 French and 500,000 German casualties. The battle of Jutland in May–June 1916 was, in Wikipedia's words, the only full-scale clash of battleships of the war, and it was indecisive.
1917: America in, Russia out
Germany adopted unrestricted submarine warfare in early 1917. The National Archives describes how British cryptographers deciphered the Zimmermann Telegram in January — a German offer to Mexico of an alliance and the "lost territory in Texas, New Mexico, and Arizona." Britain passed it to President Wilson on 24 February and it was published in the American press on 1 March. The Office of the Historian notes Wilson asked Congress for a declaration of war on 2 April and the Senate voted for it on 4 April; Congress declared war on 6 April 1917.
The US Army was small at first. Wikipedia says it had fewer than 300,000 men in April 1917; by June 1918 over 667,000 American troops had reached France, and 2 million by the end of November.
In Russia the tsar abdicated, and after the Bolshevik seizure of power the new government signed an armistice in December 1917. The two revolutions of that year are untangled in Russia in 1917.
1918: the last offensives and the Armistice
| Date | Event |
|---|---|
| 3 March | Treaty of Brest-Litovsk: Soviet Russia makes a separate peace |
| 21 March | Germany's Spring Offensive (Operation Michael) begins near Saint-Quentin, advancing 60 km |
| 15 July | Second Battle of the Marne |
| 8 August | Allied counter-attack opens the Hundred Days Offensive |
| 3 October | Prince Max of Baden becomes German chancellor and seeks terms from Wilson |
| Late October | German sailors at Wilhelmshaven and Kiel refuse to sail; revolt spreads |
| 9 November | A republic is proclaimed in Germany; Wilhelm II abdicates |
| 11 November | Armistice ends the fighting |
Wikipedia notes that the Spring Offensive, despite early success, left the German Army exhausted, and that by early November the Allies had armistices with the Ottomans and Austria-Hungary, leaving Germany isolated. The war also helped spread the influenza pandemic of 1918, the subject of the 1918 influenza pandemic.
1919 and after: when did it really end?
The fighting stopped in 1918, but a formal state of war continued. Wikipedia records that the Treaty of Versailles with Germany was signed on 28 June 1919 — five years to the day after Sarajevo — and also established the League of Nations. The US Senate never ratified it; the United States formally ended its involvement only with the Knox–Porter Resolution of 2 July 1921. Some memorials therefore date the end to 1919, while most commemorations mark 11 November 1918. Four dynasties fell: the Romanovs, Hohenzollerns, Habsburgs and Ottomans.
Long sequences like this stick better when anchored to a few fixed points; how to remember historical dates has techniques. World History Timeline Sim, our app, presents major events chronologically and lets you browse by year and region, plus timeline-ordering games for practice. Its what-if scenarios are simulations rather than history, and it is meant to support, not replace, coursework. More guides are under education and brain training.
Good to know
Frequently asked questions
When did World War I start and end?
What was the Zimmermann Telegram?
Why did Russia leave World War I early?
How many people died in World War I?
Sources
- Zimmermann Telegram (1917) (opens in a new tab)National Archives (US) — accessed
- U.S. Entry into World War I, 1917 (opens in a new tab)Office of the Historian, US Department of State — accessed
- World War I (opens in a new tab)Wikipedia — accessed
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