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The beginning.
Gavrilo Princip, a Bosnian Serb Yugoslav nationalist, assassinated the Austro-Hungarian heir Archduke Franz Ferdinand in Sarajevo, leading to the July Crisis. -
The response of Austria
In response, on 23 July, Austria-Hungary issued an ultimatum to Serbia. Serbia's reply failed to satisfy the Austrians, and the two moved to a war footing. -
when it joined the Allied Powers...
When it joined the Allied Powers after its relations with Austria-Hungary deteriorated). Russia felt it necessary to back Serbia and, after Austria-Hungary shelled the Serbian capital of Belgrade on the 28 July, approved partial mobilisation. -
Schlieffen Plan
German strategy for a war on two fronts against France and Russia was to rapidly concentrate the bulk of its army in the West to defeat France within six weeks, then shift forces to the East before Russia could fully mobilise. -
U.S declared war
the U.S. declared war on Germany on 6 April 1917. Trained American forces would not begin arriving at the front in large numbers until mid-1918.
