What was the spark that set off the explosion of world war 1?

which began in central Europe in late July 1914, included many factors, such as the conflicts and hostility between the great European powers of the four decades leading up to the war. Militarism, alliances, imperialism, and nationalism played major roles in the conflict as well. The immediate origins of the war, however, lay in the decisions taken by statesmen and generals during the July Crisis of 1914 caused by the assassination of Archduke Franz Ferdinand (the Archduke of Austria Hungary) and his wife Sophie by Gavrilo Princip, an irredentist Serb and member of the Serbian nationalist organization, the Black Hand.[1]

The crisis came after a long and difficult series of diplomatic clashes between the Great Powers (Italy, France, Germany, the British Empire, the Austria-Hungarian Empire and Russia) over European and colonial issues in the decade before 1914 that had left tensions high. In turn these diplomatic clashes can be traced to changes in the balance of power in Europe since 1867.[2] The more immediate cause for the war was tensions over territory in the Balkans. Austria-Hungary competed with Serbia and Russia for territory and influence in the region and they pulled the rest of the Great Powers into the conflict through their various alliances and treaties.