What were the causes of World War One?

On 4 August 1914, Britain declared war on Germany.

It became known as The Great War because it affected people all over the world.

The war was fought between:

  • The Triple Alliance: Germany, Austria-Hungary and their allies.

  • The Triple Entente: Great Britain, France and Russia.

Each of the countries got their troops ready to fight. Troops were groups that fought together, including the army (people who fight on land) and the navy (people who fight on the seas).

The crew of HMS Swift, a British high speed destroyer ship.
World map illustrating the Alliances and their empires before the outbreak of war in 1914.


Great Britain, Germany, Austria-Hungary and Russia all ruled many countries (colonies) across the world. They wanted to keep their empires strong and saw other countries taking over new territories as a threat.

When Germany and Austria-Hungary took control of small countries like Bosnia and Morocco, the rest of the world thought they were being aggressive.


Many countries had made alliances with one other.

They agreed to protect each other. If one was attacked, the others would defend them.

On 28 June 1914, Archduke Franz Ferdinand, the heir to the throne of Austria-Hungary, was shot and killed by a Serbian man who thought Serbia should control Bosnia instead of Austria.

Because its leader had been shot, Austria-Hungary declared war on Serbia. As a result:

  1. Russia got involved because Russia had an alliance with Serbia.

  2. Germany then declared war on Russia because Germany had an alliance with Austria-Hungary.

  3. Britain declared war on Germany because of its invasion of neutral Belgium. Britain had agreements to protect both Belgium and France.

Franz Ferdinand was murdered while visiting Sarajevo in Bosnia.

Where were battles fought?

A Mark I tank on the Western Front on 15th September 1916

War on land

Battles took place in France, Luxembourg and Belgium, called the Western Front; and in Russia, called the Eastern Front. There was also fighting on land in Italy, the Middle East and parts of Africa.

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What was trench war?

Many battles were fought using trench warfare.

Long ditches were dug in the ground. Soldiers lived in the trenches and sometimes climbed out to attack.

A famous example of trench war was the Battle of the Somme which started in July 1916.

Around one million soldiers were killed, wounded or missing.

How did life at home change?

The Defence of the Realm Act gave the government more power than it would usually have.

  • There were restrictions on pubs, bonfires and buying binoculars.

  • Feeding wild animals was seen as a waste of food so it became a crime.

  • Newspapers were stopped from writing anything that didn't support the war.

Lots of new jobs were created, such as making weapons in factories. Some women got the chance to work for the first time.

The war years affected everybody. Their lives would never be the same again.

Where next?

World War One