World War I, or as it was called at the time, the Great War, was the culmination of activity and competition between European nations. Many of the leaders of the various nations involved were personally related which made it somewhat of a 'family tiff' but a very costly one at that. Here is a list of the most commonly cited reasons for the causes of World War 1. America was decidedly isolationist throughout most of the war. However, Germany's stance of unrestricted submarine warfare that began in 1917 led to America getting involved in the war. The war began in 1914 and effectively ended with the armistice on November 11, 1918.