28 june 1914 The Balkan states of Bosnia and Herzegovina, had been annexed (took control by force) from Turkey and taken into the Austro-Hungarian Empire. This was strongly resented by many Serbs and Croats and a nationalist group, The Black Hand, was formed.
Archduke Franz Ferdinand of Austria, and his wife, had decided to inspect Austro-Hungarian troops in Bosnia. The date chosen for the inspection was a national day in Bosnia. The Black Hand supplied a group of students with weapons for an assassination attempt to mark the occasion.
A Serbian nationalist student, Gavrilo Princip, assassinated the Austrian Archduke Ferdinand and his wife, when their open car stopped at a corner on its way out of the town.
28 july 1914 The Austrian government blamed the Serbian government for the assassination of Franz Ferdinand and his wife and declared war on Serbia.
Although Russia was allied with Serbia, Germany did not believe that she would mobilise and offered to support Austria if necessary.
However, Russia did mobilise and, through their alliance with France, called on the French to mobilise.
1 agust Germany declared war on Russia
3 august Germany declared war on France. German troops poured into Belgium as directed under the Schleiffen Plan, drawn up in 1905. The British foreign secretary, Sir Edward Grey, sent an ultimatum to Germany demanding their withdrawal from the neutral Belgium.
4 august Germany did not withdraw from Belgium and Britain declared war on Germany.
The four main battles were:
The German army crossed the Belgian border on August 3rd 1914. Britain and France declared war on Germany on August 4th. The Germans pushed through Belgium, occupying Brussels before entering France.
The British and French armies marched to stop the German advance. The Battle of Marne 4th - 10th September prevented the Germans from marching on Paris.
To avoid losing the territory already...