Austrian regional security concerns grew with the near-doubling of neighboring Serbia’s territory as a result of the Balkan Wars of 1912-1913. Franz Ferdinand’s assassination in June 1914 provided the opportunity sought by some Austrian leaders for a reckoning with the smaller Slav kingdom. The Sarajevo conspirators were alleged by the Austro-Hungarian authorities to have been armed by the shadowy Black Hand, a pan-Serb nationalist grouping with links to Serbian ruling circles.
With German backing, Austria-Hungary, acting primarily under the influence of Foreign Affairs Minister Leopold von Berchtold, sent an effectively unfulfillable 15-point ultimatum to Serbia (July 23, 1914), to be accepted within 48 hours. The Serbian government agreed to all but one of the demands. Austria-Hungary nonetheless broke off diplomatic relations (July 25) and declared war (July 28) through a telegram sent to the Serbian government.
The Russian government, which had pledged in 1909 to uphold Serbian independence in return for Serbia’s acceptance of the Bosnia annexation, mobilized its military reserves on July 30 following a breakdown in crucial telegram communications between Wilhelm and Tsar Nicholas II, who was under pressure by his military staff to prepare for war. Germany demanded (July 31) that Russia stand down her forces, but the Russian government persisted, as demobilization would have made it impossible to re-activate its military schedule in the short term. Germany declared war against Russia on (August 1) and, two days later, against the latter’s ally France.
The outbreak of the conflict is often attributed to the alliances established over the previous decades – Germany-Austria-Italy vs. France-Russia; Britain and Serbia being aligned with the latter. In fact none of the alliances was activated in the initial outbreak, though Russian general mobilization and Germany’s declaration of war against France were motivated by fear of the opposing alliance being brought into play.
Britain’s declaration of war against Germany (August 4) was officially the result not of her understanding with France and Russia (Britain was technically allied to neither power), but of Germany’s invasion of Belgium, whose independence Britain had guaranteed to uphold (1839), and which stood astride the planned German route for invasion of Russia’s ally France.
The First Battles
Germany’s plan (named the Schlieffen plan) to deal with the Franco-Russian alliance involved delivering a knock-out blow to the French and then turning to deal with the more slowly mobilized Russian army. The German plan involved demanding free passage across Belgium. When this was denied, Germany invaded, occupying Luxembourg rapidly but encountering resistance before the forts of the Belgian city of Liège. Britain sent an army to France, which advanced into Belgium.
The delays brought about by the resistance of the Belgians, French and British forces and the unexpectedly rapid mobilization of the Russians upset the German plans. Russia attacked in East Prussia, diverting German forces intended for the Western Front, allowing French and British forces to halt the German advance on Paris at the First Battle of the Marne (September 1914) as the Central Powers (the German and Austro-Hungarian Empires) were forced into fighting a war on two fronts.