World War One was formally known as the Great War.
The start of the Great War began on 28th July 1914 with the shelling of Belgrade and finally ended on the 11th of November 1918.
70 million military personnel were involved in one of the biggest battles of all time.
Over 9 million servicemen were killed in during the First World War who bravely fought for their country.
In July 1914 the war started with Austria-Hungry invaded Serbia and continues through to late 1915 when the Macedonian front was formed.
During this long year, the Serbians lost over 1 million lives of both servicemen and women and civilians, Over a quarter of the population of Serbia.
On August the 1st 1914 Germany declared war on Russia and 2 days later also declared war on France.
German forces poured into Belgium on the 3rd of August 1914 and Great Britain demanded that the German troops pull out of Neutral Belgium.
The Germans refused to withdraw any troops from Belgium and Great Britain declared war on Germany on the 4th August 1914.
On the 13th of August 1914, Japan also declared war on Germany through her alliance with Great Britain from 1902.