June 28, 1914 - August 3, 1914
On June 28, 1914 Archduke Franz Ferdinand and his wife were assassinated by Gavrilo Princip. In July Austrian investigators linked the assassination to a terrorist group known as the Black Hand. This event sets in motion World War I.
The Austrians issued an ultimatum to the Serbian government. The Serbian government accepted all the terms except one, which infringed on its sovereignty. The ultimatum demanded that Austrian officials take part in any Serbian investigations of persons found in Serbian territory connected to the assassination of Archduke Franz Ferdinand.
After the Serbian government finds the Austrian's ultimatum partially unacceptable, Austria-Hungary declared war on Serbia
On 29 July the Russian government mobilized its troops to defend its Serbian ally and itself from Austria.
Another ultimatum was sent to France demanding to know what France's intentions were in case Germany went to war with Russia. The French never answered Germany's ultimatum.
Germany sends an ultimatum to Russia in which they ask Russian army to cease its mobilization immediately. The Russians replied with the answer "impossible."
After the Russian's respond to Germany's ultimatum with "impossible" the Germans decide to declare war on Russia.
German troops invade Belgium in accordance with the Schlieffen plan. The Germans failed to recognize Belgium's neutrality.
After waiting an extra two days after declaring war on Russia, the Germans no longer can wait for France's reply. Therefore Germany declares war on France.