The First World War (WWI) was fought from 1914 to 1918 and the Second World War (or WWII) was fought from 1939 to 1945. They were the largest military confrontations in human history. Both wars involved military alliances between different groups of countries. While the WWI involved the alliance system, the WWII involved the Axis Powers and the Central Powers. Periods and duration The World War 1 started from 1914 to 1918 and it lasted for 4 years. The World War II started at 1939 to 1945 and it lasted for 6 years. The two world wars have distinct periods and durations. As a comparison, the World War II lasted longer. Triggers and causes In World War I, the trigger was the assassination of Archduke Francis Ferdinand of Austria in June 1914 and the causes were militarism, imperialism, nationalism and the alliance system. In World War II, the triggers and the causes were political and economic instability in Germany after the Treaty of Versailles. The harsh conditions of the Treaty of Versailles led to the rise of power of Hitler and his alliance with Italy and Japan to oppose the Soviet Union and the Allies. As a comparison, in my opinion, World War I was more avoidable as the triggers and causes were not as sophisticated as the World War II. Conflict between In World War 1, the Central Powers (including Germany, Austria-Hungary, and Turkey) and the Allied Powers (France, Britain, Russia, Italy, Japan, and (from 1917, the U.S.) opposed each other. This is called the