Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!

Home > History > The 20th century > The First World War


The First World War




Historians disagree about what 'caused' the First World War, but most trace it in some degree to the growing power of Germany. The 'balance of power' between the nations of Europe became unstable. This led them to form military alliances:

  • The Triple Alliance ‒ Germany, Austria and Italy

  • The Triple Entente ‒ France, Britain and Russia

An easy to remember list of the most important issues surrounding the causes of the war is:

  • Militarism - many countries believed it was important to build large armies and navies.

  • Alliances - the Triple Alliance and the Triple Entente were said to have been formed to help prevent war.

  • Imperialism - European nations were creating empires and coming into conflict.

  • Nationalism - all countries were looking out for their own interests.

After the murder of Austrian Archduke Franz Ferdinand in June 1914, Austria declared war on Serbia. The countries of Europe found that the alliances they had formed dragged them into war.


In August 1914, Germany invaded France through Belgium, using its plan for war ‒ the Schlieffen Plan. The German attack was forced back at the Battle of the Marne in September 1914. Both sides dug defensive trenches and the war ground to a halt.

For the next four years, the war on the Western Front consisted of a deadly stalemate. The battles of Verdun and the Somme in 1916, and Passchendaele in 1917 were key events, where each side tried to wear the other side down.


In 1917, the Americans entered the war. Before they could arrive, the Germans made another attack, in March 1918. It was successful to start with but the Germans failed to break through. They were pushed back in August 1918. Two months later the Germans signed the Armistice [armistice: An agreement by both sides in a war to stop fighting..

Films like All Quiet on the Western Front (made in 1930 and then remade in 1979), based on the novel by Erich Maria Remarque, have led us all to imagine that we know what the First World War was like. We often think of flooded trenches, artillery bombardments, suicidal rushes across No Man's Land [no man's land: The area of land between two opposing armies., poison gas, mud and gangrene [gangrene : The death of tissue in part of the body.. There were other theatres of war, eg eastern Europe, Gallipoli, the Middle East, Africa and at sea.

The First World War was one of history's epic conflicts, and you may wish to compare it to other major wars such as the Second World War.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.