Many countries in Europe were allies and had agreements in place that they would help to defend and protect each other if they were ever attacked.
The Germans were worried that because Austria-Hungary had attacked Serbia, that Russia would attack Austria-Hungary in revenge. They therefore sent an ultimatum to Russia on 31st July 1914 demanding that they halt their military preparations within 12 hours.
With no answer received however, Germany declared war against Russia the following day on 1st August and the French began to mobilise their own army in response.
On 2nd August, Germany then sent an ultimatum to Belgium demanding that they remain neutral and not attack them whilst their troops travel through the country to fight the French in France.
On 3rd August, the Belgians rejected Germany's demands and Britain stated that they would fight to defend Belgium if it was invaded. Germany also declared war on France on this date after they failed to agree to remain neutral and not take sides in the war.
The next day, on 4th August, Germany invaded Belgium and as a result of them not providing a satisfactory explanation for doing so, Britain declared war on Germany.
Finally, on 6th August, Austria-Hungary declared war on Russia.
A world war was now taking place.
The Great War >