The First World War

By 1914 Europe was divided into two armed blocs. Germany, Austria-Hungary and Italy were linked in the Triple Alliance, though Italy would later change sides. France, Russia and Britain were bound more loosely in the Triple Entente.

Historians often summarise the deeper causes as militarism, alliances, imperial rivalry and nationalism. A naval arms race between Britain and Germany, competition for colonies, and nationalist movements inside the multinational Austro-Hungarian and Ottoman empires all raised tension. None of that made war inevitable, but it made a local crisis far more dangerous.

On 28 June 1914, Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, was shot dead in Sarajevo by Gavrilo Princip, a young Bosnian Serb linked to a nationalist group. Austria-Hungary, with German backing, sent Serbia an ultimatum designed to be hard to accept.

Russia mobilised to support Serbia. Germany declared war on Russia and then on France, and invaded neutral Belgium to reach France quickly. That invasion brought Britain into the war on 4 August. In roughly five weeks, a political murder had become a general European war.

Germany's plan to defeat France fast failed at the Battle of the Marne in September 1914. Both sides dug in, and by the end of the year a line of trenches ran from the North Sea coast to Switzerland.

Machine guns, barbed wire and massed artillery gave defenders a huge advantage. Attacks across no man's land cost enormous casualties for small gains. At Verdun in 1916 French and German forces suffered hundreds of thousands of casualties over ten months, and on the first day of the Battle of the Somme, 1 July 1916, the British army suffered about 57,000 casualties.

• On the Eastern Front, war was more mobile, and Russia suffered huge losses.
• The Ottoman Empire joined Germany; Allied forces were defeated at Gallipoli in 1915 and 1916.
• Fighting spread to Africa, the Middle East and the Pacific, and colonial troops served in large numbers.
• New weapons included poison gas, tanks, military aircraft and submarines.
• German unrestricted submarine warfare helped bring the United States into the war in April 1917.

This was total war. Governments directed industry, rationed food, recruited women into factories in large numbers and used propaganda to sustain support. Casualty lists reached almost every community.

Russia's revolutions of 1917 took it out of the war, and in early 1918 Germany launched a final offensive in the west. It failed. With American troops arriving, allies collapsing and unrest at home, Germany agreed to an armistice that took effect at 11 o'clock on 11 November 1918.

Around 9 to 10 million soldiers died, along with millions of civilians. Four empires fell: the German, Austro-Hungarian, Russian and Ottoman. New states such as Poland, Czechoslovakia and Yugoslavia appeared, and Britain and France took control of former Ottoman lands in the Middle East.

The Treaty of Versailles in 1919 blamed Germany for the war, took territory and imposed reparations. The League of Nations was founded to prevent future wars, but the United States never joined. Resentment over the peace, economic turmoil and unfinished national conflicts helped set the stage for the Second World War twenty years later.