The origins of Worl War I included many factors, including the conflicts and antagonisms of the four decades leading up to the war. The immediate origins of the war lay in the decisions taken by statesmen and generals during the July crisis of 1914, the spark (or casus belli) for which was the assassination of Archduke Franz Ferdinand of Austria-Hungary by Gavrilo Princip, a Serbian irredentist. However, the crisis did not exist in a void; it came at the end of a long series of diplomatic clashes between the Great Powers in the decade prior to 1914 which had left tensions high almost to breaking point. In turn these diplomatic clashes can be traced to changes in the balance of power in Europe since 1870.