Most historians would say that the First World War (or the Great War as it was known at the time) was caused due to a dispute between the neighbouring countries of Austria-Hungary and Serbia.
On 28th June 1914, Archduke Franz Ferdinand, who was heir to the throne in Austria-Hungary, was shot at and assassinated (murdered) whilst visiting the city of Sarejevo in Serbia in an open-top car.
Although Serbia denied any prior knowledge of the attack, Austria-Hungary requested that they apologise and gave them a set of demands (called the July Ultimatum) to fulfill within 48 hours as punishment, including the banning of any hatred towards them from their citizens and army officers.
Surprisingly, Serbia agreed to everything except the demand that members of the Austro-Hungarian government be allowed to take part in the investigation of Archduke Ferdinand's murder.
Unhappy that their demands hadn't been met in full, Austria-Hungary therefore used this as a reason for declaring war on Serbia on 28th July 1914.
The Great War >