World War I started on July 28th, 1914 and went on to last until November 11th, 1918. When WWI had its first occurrence in 1914, it was mainly called the World War, the Great War or the European War. During WWI over 9 million soldiers were killed. In WWI there were two opposite alliances, there were the Allies which consisted of Great Britain, France, Russia, and Italy and the United States later joined the war on the allied powers on April 6th, 1917. Then on the Central Powers side there was Germany and Austria- Hungary. World War I was centered in Europe and on July 28th, 1914 Austro- Hungarians fired the first shots in preparation for the invasion of Serbia. During WWI there was one major tactic that everyone was using. The name of this tactic is called Trench Warfare.