There were 18 million deaths and 23 million civilians wounded in the deadly war. From all the causes that started WW1, there was one that triggered it far enough to begin the war. WW1 lasted from year 1914 to 1918 and had many reasons that caused the bloody war. The top five reasons of the war was Mutual Defense Alliances, Imperialism, Militarism, Nationalism, and the Assassination of Archduke Franz Ferdinand.
The Mutual Alliance Imperialism was a cause because of countries defending a nation that another nation is against and the hate goes around and the countries choose a side. The country states that were involved in the fight were: United Kingdom, France, Russia, Italy, United States of America, Germany, Austria-Hungary,