Causes for World War I Many things led up to the start of World War I. There was much tension between the countries of Europe for more than fifty years. There were immediate causes, and long-term causes. Some immediate causes were the assassination of the heir of Austria-Hungry, Germany declaring war on Russia, Germany declaring war on France, and Great Britain declaring war on Germany. Some long-term causes or basic causes were imperialism, nationalism, and the arms race. The assassination of Archduke Frances Ferdinand, who was the heir to the throne of Austria-Hungary, was probably the last step on the long road to war. A Serbian patriot murdered Ferdinand in Sarajevo, on June 28 1914