Assassination of Archduke Franz Ferdinand of Austria
The Archduke Franz Ferdinand of Austria was making a visit to Sarajevo with his wife on June 28, 1914.Thy ended up being assassinated while there by a terrorist group, Black Hand, and led to Austria declaring war on Serbia and Germany over Russia.
Countries agreed to signing mutual defense agreements with nations they could mutually depend on in the face of war. Russia-Serbia and Germany-Austria-Hungary were already in alliances and they had further alliances adding more nations in the conflict.
Nationalism played a role in leading to the war not only in the Balkan region. The entire Europe was focused on the concept of nationalism, giving each of nations an ‘inviolable territory’. So when Germany had captured Alsace-Lorraine in 1871, it did not go very well with the French.
The major European powers had colonies all around the world. The British had control over major parts of South Asia, the French were colonizing a lot of Africa and the Spanish started colonizing parts of South America under their rule.
Allied forces halt German advance into France during First Battle of the Marne.
German submarine sinks the Lusitania during crossing from New York to Liverpool, England, killing 128 Americans.