What was the spark that caused the First World War?

The causes of World War 1, which began in central Europe in late June 1914, included intertwined factors, such as the conflicts and hostility of the four decades leading up to the war. militarism, alliances, imperalism, and national played major roles in the conflict as well. However, the immediate origins of the war lay in the decisions taken by statesmen and generals during the Crisis of 1914, casus belli for which was the assasination of archduke Franz Ferdinand of Australia and his wife by Gavrilo Princip, an irredentist Serb