World War I (abbreviated WWI or WW1) was a global war that was started in Europe on July 28, 1914. This war lasted for over four years, finally coming to an end on November 11, 1918. This war was not only long, but it was also one of the largest wars in history. Over 70 million military personnel were mobilized, including 60 million Europeans. This war was also very deadly, resulting in the death of approximately 9 million servicemen and 7 million civilians.
The first event that led to the war was the assassination of Archduke Franz Ferdinand by Gavrilo Princip. Following the assassination, Serbia and Austria-Hungary went to war. The war grew as a result of interlocking alliances. Europe was divided into two coalitions: the Triple Alliance and the Triple Entente. Then, a domino effect began. Russia was ready to defend Serbia, its ally. Then, Germany declared war on Russia in order to protect Austria. France in turn declared war on Germany to protect Russia. Then, Britain declared war on Germany after the Germans invaded Belgium. On one side, the countries that were involved in this war included Austria-Hungary, Bulgaria, Germany, and the Ottoman Empire. Fighting against them was France, Great Britain, italy, Japan, Romania, Russia, and the United States. The war finally came to an end in 1917 with the signing of the Treaty of Versailles.
Austria-Hungary, Bulgaria, Germany, and the Ottoman Empire fought against France, Great Britain, Italy, Japan, Romania, Russia, and the United States in World War I.
Eleven countries were involved in World War I, which started in 1914.