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The Triple Alliance is Formed
In 1882 Germany, Austria-Hungary and Italy formed the Triple Alliance. The three countries agreed to support each other if attacked by either France or Russia. -
Triple Entente is formed
The Triple Entente is an informal coalition between Great Britain, France and Russia, now countered the Triple Alliance. International tension was greatly increased by the division of Europe into two armed camps. -
Austria-Hungary Takes Control of Bosnia
Bosnia and Herzegovina were still nominally under the control of the Ottoman Sultan in 1908. In January 1909, at the height of the Bosnia-Herzogovina crisis, Franz Conrad von Hotzendorff, the chief of staff of the Austrian army, approached Helmuth von Moltke, his German counterpart, to ask what Germany would do if Austria invaded Serbia and thus provoked Russia to intervene on the latter’s behalf. -
Archduke Franz Ferdinand is Assassinated in Sarajevo
Immediately following the assassination Germany pledged its full support to Austria-Hungary, pressuring them to declare war on Serbia. Austria-Hungary issued Serbia an unacceptable ultimatum, to which Serbia consented almost entirely. -
Austria-Hungary Declares War on Serbia
Austria-Hungary declared war on Serbia. In response, Russia formally ordered mobilization in the four military districts facing Galicia, its common front with the Austro-Hungarian Empire. On August 1, after its demands for Russia to halt mobilization met with defiance, Germany declared war on Russia. Russia's ally, France, ordered its own general mobilization that same day, and on August 3, France and Germany declared war on each other. -
Primary Source
http://www.history.com/this-day-in-history/austria-hungary-declares-war-on-serbia When Austrian artillery divisions initiated a brief, ineffectual bombardment of Belgrade across the Danube River.
British naval official Winston Churchill wrote to his wife at midnight, "My darling one and beautiful, everything tends towards catastrophe and collapse," -
Germany Invades Belgium
Belgium was neutral and its neutrality was protected by treaty with Great Britain. The Germans attacked on August 3rd. The next day, Great Britain declared war on Germany. -
A German U-Boat Sinks the Lusitania
The Lusitania carried a healthy complement of American passengers when she departed New York for Liverpool on May 1, 1915. The lost of the Lusitania marked the end of any delusions that the "civilized" manners of 19th century warfare could survive into the 20th. -
The First Battle of the Somme Begins
Battle of the Somme is famous chiefly on account of the loss of 58,000 British troops (one third of them killed) on the first day of the battle. The attack was launched upon a 30 kilometre front, from north of the Somme river between Arras and Albert, and ran from 1 July until 18 November, at which point it was called off. -
The Zimmerman Telegram
Zimmerman was assuming America would soon declare war on Germany anyway because, as was mentioned in his telegram, the Kaiser's navy was about to revive its policy of "unrestrained submarine warfare" It was intercepted by the British and its contents hastened the entry of the United States into the war. The British had intercepted the telegram as the message passed along American-owned cables through London to Johann von Bernstorff, the German ambassador in Washington, on Jan 16. -
The United States Declares War on Germany
Opinion against Germany hardened after the sinking of the Lusitania. William Jennings Bryan, the pacifist Secretary of State, resigned and was replaced by the pro-Allied Robert Lansing. On 31st January, 1917, Germany announced a new submarine offensive. Wilson responded by breaking off diplomatic relations with Germany
