What was the main causes of the First World War?

The causes of the First World War are numerous and varied, with long and short term factors but the main reason was the formation of Germany threatening the Balance of Power of Europe. Britain's foreign policy for centuries has been to ensure one nation could not become the hegemon of Europe and ensure the balance between the different nations of Europe. When Germany united in 1871 through military force, this balance was threatened especially as over the 1870's and 1880's Germany rapidly industrialised gradually overtaking Britain at the start of the Twentieth Century. As Wilhelm II ascended to the German throne in 1888, Germany abandoned the cautious foreign policy of Bismarck in favour of a conventical European states. This led to Britain, France and Russia forming the Triple Entente out of fear of Germany's economy and very competent military while attempting to preserve the European balance of power. While short term events such as the annexation of Bosnia, the two Moroccan crisises and the assassination of Franz Ferdiand did help to set events into motion, the unification of Germany and its adoptation of a conventional European foreign policy was the main cause of the First World War.