http://www.theweek.co.uk/world-news/first-world-war/59782/how-did-the-first-world-war-start
http://www.greatwar.co.uk/timeline/ww1-timeline.htm
http://www.un.org/apps/news/story.asp?NewsID=45909#.WLV83fkrLIU
http://www.ducksters.com/history/world_war_i/
World War I lasted over four years and finally came to an end when Germany surrendered on November 11th, 1918 and all nations agreed to seize fighting while the terms of peace where negotiated. A peace treaty, the Treaty of Versailles was signed by Germany and the Allied Nations in 1919. This war claimed 17 million lives and caused mass amounts of damage.
When WWI broke out, President Woodrow Wilson placed the United States as neutral in the war. However, in 1915, the Lusitania, a British liner was taken down by a German submarine and killed 128 Americans. This furthered tensions and by the end of 1915, Austria-Hungary, Bulgaria, Germany, and the Ottoman Empire were battling the Allied Powers of Britain, France, Russia, Italy, Belgium, Serbia, Montenegro and Japan. On April 6th, 1917, the United States entered World War I and declared war on Germany.
When Austria-Hungary declares war on Serbia, Britain calls for international mediation. Russia and Germany begin to warn one another and both mobilize. Then Germany declares war on Russia. Belgium and France begin to mobilize then Germany declares war on France and invades Belgium.
Britain then declares war on Germany and Austria-Hungary then declares war on Russia. Then France and Britain declare war Austria- Hungary. As we can see, the assassination began a spiral of events that divided the world into two sides.
By 1914, Europe was split into two sides, the Allies and the Central Powers.
The Allies:
June 28, 1914: The immediate cause of WWI was the assassination of Franz Ferdinand,heir to the Austrian throne, of Austria- Hungary by a Serbian nationalist, Gavrilo Princip. Austria- Hungary then declared war on Serbia. This created a domino effect that turned into a world war.
The Central Powers: