Humanity's first global military conflict. Two coalitions met on the battlefields — the Central Powers and the Entente. Over four years roughly 17 million people died, four empires collapsed (the German, the Austro-Hungarian, the Russian, and the Ottoman), and the map of Europe was reshaped forever. The contradictions baked into the 1919 settlement detonated twenty years later as the Second World War.
Who fought whom
Central Powers: the German Empire (Kaiser Wilhelm II), Austria-Hungary (Emperor Franz Joseph I, from 1916 — Charles I), the Ottoman Empire (Sultan Mehmed V) and Bulgaria (Tsar Ferdinand I).
Entente (Allies): France (from 1917 — Premier Georges Clemenceau), the United Kingdom (David Lloyd George), the Russian Empire (Nicholas II — until 1917), Italy (from May 1915, Premier Vittorio Emanuele Orlando), the United States (from April 1917, President Woodrow Wilson). They were joined by Serbia, Belgium, Japan, Greece, and Romania.
In all, more than 30 countries took part; about 70 million soldiers were mobilised.
Phases of World War I
The war was fought on several theatres at once — the Western Front (France, Belgium), the Eastern Front (Poland, Ukraine, the Balkans), the Italian Front, the Middle East, Africa, and at sea. We will go year by year: 1914 — how it began, 1915 — globalisation, 1916 — the heaviest bloodletting, 1917 — the turning point, 1918 — the end. We will look separately at trench life, new weapons, and the colonial theatres.
1914: the assassination that started it all
On 28 June 1914 a 19-year-old Serbian nationalist, Gavrilo Princip, a member of the "Young Bosnia" group, shot dead Archduke Franz Ferdinand — heir to the Austro-Hungarian throne — and his wife Sophie in Sarajevo. 28 June is St Vitus's Day (Vidovdan), a Serbian national holiday and the symbolic anniversary of the 1389 Battle of Kosovo.
Austria-Hungary blamed Serbia for the killing and issued a ten-point ultimatum. Serbia accepted almost all of it — except admitting Austrian investigators onto its soil. On 28 July 1914 Austria declared war on Serbia. Through the chain of alliances, all the great powers of Europe were dragged in within a week.
The Schlieffen Plan and the invasion of Belgium
Germany held to the Schlieffen Plan, drafted back in 1905: smash France quickly through neutral Belgium and the Netherlands, then swing the troops east against Russia. The plan called for taking Paris in 42 days.
On 4 August 1914 the Germans crossed the Belgian border. Belgian resistance at Liège held them up for a week. The United Kingdom, guarantor of Belgian neutrality under the 1839 treaty, declared war on Germany the same day. The conflict had become global.
The Miracle on the Marne and Tannenberg
In the east, on 26–30 August 1914, Paul von Hindenburg (a 67-year-old retired general called back to service) and his chief of staff Erich Ludendorff destroyed Alexander Samsonov's Russian 2nd Army at Tannenberg. Samsonov shot himself in a forest. Hindenburg became a national hero; eighteen years later he would become President of Weimar Germany and appoint Hitler chancellor.
In the west, on 6–12 September 1914, the French under Joseph Joffre halted the Germans 30 km from Paris — the "Miracle on the Marne". The military governor of Paris, Gallieni, commandeered 600 Paris taxis to rush the 6th Army to the front — history's first mass motorised troop transfer. The Schlieffen Plan had failed.
Trenches and the Christmas Truce
After the Marne the war turned into a four-year trench slaughter. The front line stretched from Switzerland to the North Sea — a continuous belt of trenches, barbed wire, machine-gun nests, millions of shells, and no one able to break through.
At Christmas 1914 an unofficial fraternisation broke out on the Western Front: about 100,000 German and British soldiers held their fire, swapped cigarettes and chocolate, and played football between the trenches. Commanders banned any repeat — and in the following years such scenes barely happened again. In the same sector around Ypres, only a few months later, the war's first mass gas attack would take place.
The Russian army in Galicia
While Tannenberg unfolded in the north, on the South-Western Front the Russian army under Ivanov broke the Austro-Hungarian forces in the Battle of Galicia (August–September 1914). On 3 September the Russians took Lviv and the whole of Eastern Galicia. The Austrians lost 400,000 men, including 100,000 prisoners — a catastrophe the empire never recovered from.
The Russian occupation of Galicia came with russification: Metropolitan Andrey Sheptytsky was arrested and exiled to Suzdal, Ukrainian schools and societies were shut down. The occupation left a deep mark on Ukrainian–Russian relations for decades to come.
1915: gas, the first ship victims, new players
On 22 April 1915 at Ypres in Belgium the Germans used chlorine gas for the first time in the history of warfare: 168 tonnes were released from 5,730 cylinders against French-Algerian positions. The first 6,000 soldiers suffocated within minutes. The 1899 Hague Convention formally banned chemical weapons, but chlorine was released from cylinders rather than fired from shells — a technical loophole.
The development was overseen by the German chemist Fritz Haber, a future Nobel laureate. His wife Clara, herself a chemist, shot herself in protest a week later.
Gallipoli — a botched attempt to knock Turkey out of the war
First Lord of the Admiralty Winston Churchill proposed seizing the Dardanelles — the strategic strait between the Aegean and the Sea of Marmara. The idea was logical: knock the Ottoman Empire out of the war and open a sea route to Russia.
The landings began on 25 April 1915. The Turkish defence was organised by 34-year-old Colonel Mustafa Kemal (the future Atatürk), who told his soldiers the legendary line: "I am not ordering you to attack — I am ordering you to die." After nine months of fighting, the Entente lost 220,000 men and evacuated in January 1916. Churchill was removed from his post. The ANZAC (Australian and New Zealand Army Corps) lost 11,000; 25 April is still commemorated as ANZAC Day.
The Lusitania, Italy, the Great Retreat
On 7 May 1915 the German submarine U-20 torpedoed the British passenger liner Lusitania off the Irish coast. 1,198 people were killed, 128 of them American. The outrage in the United States was one of the factors that pushed America toward joining the war.
On 23 May 1915 Italy declared war on Austria-Hungary and joined the Entente — under the secret Treaty of London, which promised it Trentino, South Tyrol, Trieste, and part of Dalmatia.
On the Eastern Front, in May–September, the German-Austrian breakthrough at Gorlice forced the Russians into the Great Retreat: Poland, Galicia, and parts of Lithuania and Belarus were lost. Tsar Nicholas II personally took over Stavka — a fatal mistake that put him face to face with every defeat.
The Armenian genocide
On 24 April 1915 around 250 Armenian intellectuals were arrested in Constantinople. This marked the start of the Armenian genocide — the first mass genocide of the 20th century. The "Young Turks" (Enver, Talaat, Cemal) accused Armenians of sympathising with Russia after the defeat at Sarikamish; deportations and mass killings followed.
By 1918 around 1.5 million Armenians had been killed — roughly 75% of the entire Armenian population of the Ottoman Empire. Jewish memory of the Khmelnytsky pogroms ("gzeyrot tach ve-tat") and Armenian memory of the 20th-century genocide became two great precedents of "genocide memory" in world culture. Turkey still does not officially recognise the events as genocide.
1916: the year of the heaviest bloodletting
The chief of the German General Staff, Erich von Falkenhayn, set out to "bleed France white": attack the symbolic fortress of Verdun, which the French would defend to the last. The blow fell on 21 February 1916. The French gave command of the 2nd Army to Philippe Pétain, with the slogan "Ils ne passeront pas" — "They shall not pass."
The battle lasted 302 days — the longest battle of the First World War. About 700,000 casualties on both sides. The French held Verdun thanks to the "Sacred Road" (Voie sacrée), used to rotate units in and out. In 1940 the 84-year-old Pétain would head the collaborationist Vichy regime — the national hero of 1916 became the curse of 1945.
The Somme and the debut of the tank
The Allies planned a major offensive on the river Somme to relieve the pressure on Verdun. 1 July 1916 — the first day of the battle — became the bloodiest day in the history of the British Army: 57,000 casualties in twenty-four hours, almost 20,000 of them killed. Whole streets and villages in Britain were widowed in a single day (the "Pals' Battalions" — volunteers from one town serving together).
On 15 September 1916 the Somme saw the combat debut of the tank — the British Mark I, a secret Admiralty project under Churchill. The codename "tank" came from a deception (these were supposedly water tanks). 49 machines, 6 km/h, a crew of eight — many bogged down in the mud, but the psychological effect was devastating. By 1918 Britain had over 2,600 tanks.
Jutland and the Brusilov Offensive
On 31 May – 1 June 1916 the Battle of Jutland was fought in the North Sea — the only major naval battle of the First World War, between the British Grand Fleet and the German High Seas Fleet. Tactically the Germans sank more British ships (14 to 11), but strategically the German fleet never put to sea again. The British blockade of Germany held until the end of the war.
In the east Aleksei Brusilov tried a new tactic — simultaneous attacks on several sectors without a long preparatory bombardment. The Brusilov Offensive (June–September 1916) shattered the Austro-Hungarian armies, took 400,000 prisoners, and brought Austria-Hungary to the brink of collapse. It was the most successful Entente offensive of 1916. After 1917 Brusilov went over to the Bolsheviks and served in the Red Army.
The Easter Rising in Dublin
While Europe traded blows, Ireland flared up in the Easter Rising (24–29 April 1916). Irish republicans led by Patrick Pearse and James Connolly seized the General Post Office in Dublin, proclaimed an Irish Republic — and lost in six days.
The British executed 15 of the leaders. The badly wounded Connolly could not stand — he was tied to a chair before being shot. Those executions turned an initially unpopular rising into a story of martyrs, and set off the chain of events that led to Irish independence in 1922.
1917: the year of two revolutions and the entry of the United States
In the Russian Empire, hunger, inflation, and distrust of the Romanov dynasty (especially because of Rasputin) had piled up. On 8 March 1917 women's demonstrations in Petrograd grew into a general strike. The Petrograd garrison refused to fire on the crowds. On 15 March, Tsar Nicholas II abdicated — 304 years of Romanov rule had ended.
The Provisional Government kept the war going — a fatal mistake that opened the way for the Bolsheviks in October. The tsar first abdicated in favour of his brother Mikhail Alexandrovich, but he too refused the next day. On the night of 16–17 July 1918 the Bolsheviks would shoot the entire imperial family in the basement of the Ipatiev House in Yekaterinburg.
The Zimmermann Telegram and the entry of the United States
In January 1917 the German foreign minister Arthur Zimmermann sent the German ambassador in Mexico an encrypted telegram: a proposal to Mexico for an alliance against the United States in exchange for the return of Texas, Arizona, and New Mexico.
The British codebreakers in Room 40 deciphered the text within days. The British spent a month inventing a plausible story for how they had come by it (so as not to reveal that they were breaking German codes), and on 24 February they passed it to the Americans. On 1 March the telegram was published in the press. On 6 April 1917 Congress declared war on Germany. By November 1918 two million American soldiers had reached Europe — the decisive factor in Germany's defeat.
After the war Room 40 evolved into the Government Code and Cypher School (GC&CS) — the predecessor of Bletchley Park and modern GCHQ. The American Expeditionary Forces in France were led by John Pershing, who insisted on using American forces as an independent army rather than as "filler" for European armies.
Passchendaele, Caporetto, and the Balfour Declaration
On the Western Front the British commander Douglas Haig launched the Third Battle of Ypres on 31 July 1917 — better known as Passchendaele — to break through to the Belgian coast. 100 days of fighting in the mud, around 500,000 Entente casualties for an advance of 8 km. In 1918 the Germans took back everything that had been lost in a few days. Passchendaele became a symbol of strategic futility.
On the Italian Front, on 24 October 1917, Austro-German forces (including a young lieutenant named Erwin Rommel) routed the Italian army at Caporetto. 11,000 killed, 265,000 captured, a 150 km retreat. In Italian, "caporetto" became a synonym for catastrophe.
On 2 November 1917 the British foreign secretary, Arthur Balfour, in a letter to Lord Rothschild, promised support for the establishment of "a national home for the Jewish people" in Palestine — the Balfour Declaration, the foundation stone of the future State of Israel (1948). The declaration contradicted simultaneous British promises of independence to the Arabs — a source of conflict to this day.
The October Revolution and Russia's exit from the war
On the night of 6–7 November 1917 (25 October Old Style) the Bolsheviks under Vladimir Lenin seized power in Petrograd. The next day the Second All-Russian Congress of Soviets adopted the Decree on Peace — a proposal to all the warring powers to conclude an immediate peace without annexations or indemnities.
The Entente refused to negotiate — and the Bolsheviks were forced to seek a separate peace with the Central Powers. As head of the delegation, Leon Trotsky pursued the line of "neither war nor peace". When the Germans resumed their advance in February 1918, the Bolsheviks accepted harsh terms which Lenin called "a humiliating peace".
1918: Wilson's Fourteen Points and the Brest-Litovsk Treaty
On 8 January 1918 US President Woodrow Wilson set out before Congress his famous Fourteen Points — a programme for the post-war order: open diplomacy, freedom of the seas, the self-determination of peoples, the creation of a League of Nations. It was the first systematic plan for a world order.
On 3 March 1918, in Brest-Litovsk (today Brest in Belarus), Soviet Russia signed a separate peace with the Central Powers. Russia lost Ukraine, Poland, the Baltic provinces, Finland, and the Caucasus — about a third of its population and 90% of its coal. The treaty was annulled in November 1918 after Germany's surrender, but by then the Russian Civil War had begun, and the lost territories had passed into the hands of new independent states.
The Kaiserschlacht — Germany's last attempt
The Brest-Litovsk Treaty allowed Germany to transfer 50 divisions from the Eastern to the Western Front. Ludendorff wanted to win the war before the bulk of the American forces arrived. The Spring Offensive (Kaiserschlacht — "the Kaiser's Battle") opened on 21 March 1918 with Operation Michael.
Germany used a new tactic — stormtroopers (Stoßtruppen): small groups infiltrating deep into the defences instead of mass frontal assaults. This was the prototype of the blitzkrieg the Wehrmacht would use in 1939. In four months the Germans advanced 60 km — more than the Entente had managed in all the previous years. But Germany was running out of reserves: troops were exhausted, food was running short because of the British naval blockade (the "Turnip Winter" of 1916–1917 in Berlin had taken some 700,000 civilian lives to starvation).
The Hundred Days Offensive and the surrender
On 15 July 1918 the Second Battle of the Marne stopped Germany's last advance. The Entente seized the initiative. From 8 August 1918, under Marshal Ferdinand Foch, the Hundred Days Offensive began — a string of victories that ended in the armistice. Ludendorff called the first day, at Amiens, "the black day of the German army".
On 9 November Chancellor Max von Baden announced the abdication of Kaiser Wilhelm II (without his consent). The Kaiser fled to the Netherlands, where he died in 1941. The Weimar Republic was proclaimed.
At 5:45 a.m. on 11 November 1918, in the forest of Compiègne, in Foch's personal command railway carriage, the Armistice of Compiègne was signed. At 11:00 — ceasefire. The end of the Great War.
That same carriage was brought back to the forest of Compiègne by Hitler in 1940 for symbolic revenge — France's surrender on the same spot.
Versailles and Article 231
The Paris Peace Conference, beginning in January 1919, shaped the new world order. The Big Four — Wilson (United States), Clemenceau ("the Tiger" of France), Lloyd George (Britain), and Orlando (Italy) — settled the terms over six months. Orlando demonstratively walked out of the talks when Italy was refused Fiume and Dalmatia (hence the "vittoria mutilata" — the "mutilated victory" that fed Mussolini's fascism).
On 28 June 1919 — exactly five years after the killing of Franz Ferdinand — in the Hall of Mirrors at the Palace of Versailles (where the German Empire had been proclaimed in 1871) the Treaty of Versailles was signed. Article 231 — the "war guilt clause" — placed sole responsibility for the war on Germany. Reparations: 132 billion gold marks. The loss of 13% of its territory and all of its colonies. The army was capped at 100,000. Air forces and tanks were forbidden.
Marshal Foch said prophetically of Versailles: "This is not peace. It is an armistice for twenty years." His words came true in 1939.
Trench life
The real enemy of the soldier on the Western Front was not the enemy machine gun but the filth of daily life. Rats the size of cats, gnawing at the bodies of the dead; lice carrying trench fever (Bartonella quintana — only identified in the 1960s); and water permanently up to the ankles.
Trench foot — tissue rotting from constant damp. Gas gangrene — from anaerobic bacteria in the soil. More than a million Entente soldiers caught trench fever. One of the first documented cases was the writer J. R. R. Tolkien, a Somme veteran, whom the illness sent home from the front in 1916.
The New Zealand surgeon Harold Gillies set up a hospital in Sidcup where, in four years, around 11,000 reconstructive operations were performed — a literal birth of plastic surgery as a science.
New weapons: gas, tanks, aircraft
The First World War was a testing ground for technologies that would reshape the 20th century. Chemical weapons — chlorine, phosgene, mustard gas. By the end of the war the two sides had used 124,000 tonnes of toxic agents, causing more than a million casualties.
Tanks — debut on 15 September 1916 at the Somme. The first big battle with mass tank use was Cambrai (1917), with 476 machines. Germany only built its A7V by 1918 (just 20 vehicles in all); Versailles forbade it tanks, so it secretly developed them in the USSR from 1924 to 1933.
Aircraft — the first aerial combat took place in October 1914. The German ace Manfred von Richthofen ("the Red Baron", commander of the "Flying Circus") scored 80 aerial victories before being killed on 21 April 1918, aged 25, over the Somme. Germans and British bombed London and Paris with zeppelins; Britain in response set up the first dedicated air-defence units.
Women, animals, and poets
Before the war women in Britain and France did almost no factory work. By 1916 around 950,000 women were working in British munitions plants — they were called the "canary girls", because their skin, hair, and even their children turned yellow from exposure to TNT. Over 400 died from poisoning and explosions. In February 1918 Britain gave the vote to women aged 30 and over.
Around 16 million animals were taken to war. The carrier pigeon Cher Ami, in October 1918 during the Meuse-Argonne offensive, saved the "Lost Battalion" — flying 40 km with a wounded chest, awarded the Croix de Guerre. The pigeon's stuffed body is still on display at the Smithsonian.
The poet Wilfred Owen, author of "Dulce et Decorum Est", was killed on 4 November 1918 — seven days before the armistice — crossing the Sambre-Oise canal. His mother received the death telegram while the bells of London were ringing for peace.
Beyond Europe: Mesopotamia, Africa, Arabia
The Mesopotamian campaign (1914–1918) — British-Indian troops against the Ottomans in present-day Iraq. The landings at Basra (November 1914) were intended to protect the pipelines of the Anglo-Persian Oil Company. The disaster at Kut-al-Amara in April 1916 (13,000 prisoners — the largest British surrender before Singapore in 1942). The capture of Baghdad in March 1917 — "we come as liberators, not as conquerors". After the war the San Remo conference of 1920 placed Iraq under a British mandate.
The East African campaign (1914–1918) — the longest guerrilla war of the First World War. Colonel Paul von Lettow-Vorbeck, with 14,000 mostly African soldiers (askaris), fought against around 300,000 Allied troops in German East Africa (modern Tanzania). Undefeated in the field for four years, he surrendered on 25 November 1918, fourteen days after the armistice (which at first he did not believe).
Lawrence of Arabia and colonial troops
The British officer-archaeologist T. E. Lawrence from 1916 helped organise the Arab Revolt against the Ottomans. He led the capture of Aqaba (July 1917) and Damascus (October 1918) at the head of Arab cavalry. He grew bitter when Britain and France carved up the Middle East under the secret Sykes-Picot Agreement of 1916, instead of granting the Arabs the independence they had been promised. He wrote his "Seven Pillars of Wisdom" (1926) partly out of guilt. He died in a 1935 motorcycle crash — and it was that very case that prompted the invention of the protective helmet for motorcyclists.
About 2.5 million soldiers from the colonies and dominions fought in Europe — Indian sepoys (around 1.4 million), Senegalese tirailleurs, Algerians, Vietnamese, Australians, New Zealanders, Canadians. Their names often dropped out of the statistics, but without them the war simply could not have been waged. The experience of colonial mobilisation undermined the imperial hierarchy — soldiers came home with a new sense of themselves. This became one of the drivers of the next wave of decolonisation.
What was left after the war
The First World War destroyed four empires: the German, the Austro-Hungarian, the Russian, and the Ottoman. In their place new states arose: Poland, Czechoslovakia, Yugoslavia, Austria, Hungary, Turkey, the independent Baltic states and Finland, and the Soviet Union (from 1922).
Versailles was only the first of five peace treaties: with Austria (Saint-Germain, September 1919), with Bulgaria (Neuilly, November 1919), with Hungary (Trianon, June 1920 — Hungary lost two-thirds of its territory, a trauma still felt today), and with the Ottoman Empire (Sèvres, August 1920 — never ratified, because of the Turkish war of independence).
In 1918–1920 the planet was hit by the Spanish flu (the H1N1 virus) — a third of humanity fell ill and 50–100 million died. That was more than all the combat losses of the war put together. The name "Spanish" came from the fact that neutral Spain alone did not censor reports of the disease.
The seeds of the Second World War
Versailles bred in Germany a sense of unjust humiliation — the "Diktat of Versailles". Article 231 (sole German guilt) and 132 billion in reparations were fertile ground for a nationalist reaction. In 1923 Ludendorff took part in Hitler's Beer Hall Putsch in Munich.
The United States, despite its president's role at Versailles, refused to ratify: the Senate did not approve the treaty, and the United States never joined the League of Nations — Wilson's own idea. For the last 17 months of his presidency Wilson, paralysed by a stroke, did not appear before his cabinet — the country was effectively run by his wife Edith.
Marshal Foch had been right. Twenty years later, on 22 June 1940, Hitler brought the same railway carriage in which Germany had surrendered in 1918 back to the forest of Compiègne — to accept the surrender of France in it. The First World War did not end at Versailles. It only paused.
Now you have the general picture. Try a question session — you will see how it all fits together.