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World War One was the first truly global conflict. In the wake of the assassination of Archduke Franz Ferdinand on 28 June 1914, the declarations of war began. Gradually, the war drew in countries from all across the globe and nations continued to enter the war until the day before the Armistice.
28 July 1914: Austria declares war on Serbia
Austrian commanders pressured their government into issuing an ultimatum to Serbia. While Serbia agreed to most of their demands, the stipulation that Austria carry out an investigation into the assassination of the archduke undermined the Serbian judicial system and was therefore considered incompatible with the maintenance of Serbian sovereignty.
Having agreed to every other demand, Serbia suggested that the investigation be referred to an international tribunal in the Hague.
Despite Serbia’s apparent acquiescence, the Austro-Hungarian Empire, believing it had firm German backing, declared war on its Balkan neighbour. The First World War had begun.
1 August 1914: Germany and Russia declare war on each other
Russia began mobilising its troops in response to the Austrian declaration of war against Serbia, Russia’s ally in the Balkans.
Germany demanded that Russia cease mobilisation but the Tsar was informed that demobilising Russian forces at this point would be very costly and would leave the extremities of the Russian Empire vulnerable.
As a result, Germany declared war on Russia on 1 August.
3 August 1914: Germany and France declare war on each other
The French, allied to Russia, refused to abide by Germany’s request that they remain neutral. Instead, the French began to mobilise their reserves and pulled their existing forces back from the French-German border to avoid any unforeseen incidents.
Following an attack on Luxembourg on 2 August 1914, Germany made a formal declaration of war against France on 3 August 1914.
4 August 1914: Germany declares war on Belgium and the United Kingdom declares war on Germany
The Germans planned to invade France quickly and decisively, knocking them out of the war in order to focus all efforts on their Russian frontier, a strategy known as the Schlieffen plan.
The Schlieffen plan called for an invasion of France through Belgium. When the Belgian government denied Germany’s request to advance through the country, Germany declared war on Belgium.
Germany had been eager to keep Britain neutral. But Britain had guaranteed Belgian neutrality in the Treaty of London in 1839, so the British government had little choice but to enter the war.
6 August 1914: Austro-Hungary declares war on Russia
Austro-Hungary declared war on Russia, moving troops to their Russian frontier to ensure the Russians could not overrun their eastern flank. It remained focused on the invasion of Serbia.
From this point until late August 1914 a series of further declarations established the two warring sides in Europe. The Allied Powers, including Britain, France, Belgium, Russia and Serbia, faced off against the Central Powers, led by Germany and Austria-Hungary.
The escalation continued later in the year with the entry of Japan, in support of the Allies, and on 1 November the Ottoman Empire, who entered the war with the Central Powers.