At the dawn of the 20th century, few anticipated a global war, but what came to be known as the Great War began on June 28, 1914, with the assassinations of Austrian Archduke Franz Ferdinand and his wife, Sophie, while they were visiting Sarajevo, Bosnia, a country recently annexed into the Austrian Empire.
The First World War saw the Entente Powers, led by France, Russia, the British Empire, and later Italy (from 1915) and the United States (from 1917), defeat the Central Powers, led by the German, Austro-Hungarian, Bulgarian and Ottoman Empires.
Empires were seen as an expanding power, administration, ideas and beliefs followed by cultural habits from place to place. Some empires tended to impose their culture on the subject states to strengthen the imperial structure; others opted for multicultural and cosmopolitan policies.
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:
Russia got involved because Russia had an alliance with Serbia.
Germany then declared war on Russia because Germany had an alliance with Austria-Hungary.
Britain declared war on Germany because of its invasion of neutral Belgium. Britain had agreements to protect both Belgium and France.
Battles were fought on land, in the air and at sea. 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.
Naval battles mainly took place in the North Sea and the Atlantic. Britain used blockades to stop Germany from receiving supplies by sea. Germany reacted by using U-boats (submarines) to attack ships travelling to Britain.
Aeroplanes were new at this time. There were three different types of aircraft: Scouting, used for fighting; Bombers; and Reconnaissance, used for photography and directing artillery.
Many battles were fought using trench warfare.
Long ditches were dug in the ground. Soldiers lived in these trenches and sometimes climbed out to attack.
A famous example of trench warfare was the Battle of the Somme. It lasted from July to November 1916. Around one million soldiers were killed, wounded or missing in the battle.
On the Western Front, soldiers on both sides lived in trenches.
Trenches were long, narrow ditches dug into the ground.
They were very muddy.
Some soldiers developed a problem called trench foot.
In the middle was no man's land. Soldiers crossed this to attack the other side.
The Defence of the Realm Act gave the government more power than it would usually have.
There were restrictions on bonfires, pubs, 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 have paid jobs for the first time.
The war years affected everybody. Their lives would never be the same again.