World War I was not a consequence of a single event. Though there were several factors that led to the development of the Great War but above all, it was triggered because of the tensions between the European powers and the crisis of the balance-of-power system which led to the division of Europe into two camps.
While one camp, comprising of Russia, Great Britain and France, together called as Triple Entente endeavored to preserve the flimsy balance between great European powers, the second camp of German Empire, Italy and Austria- Hungry was opposing it.
Mentioned below are specific 7 events that fueled the World War 1, which is one the most devastating military conflicts our history has ever witnessed.
The war that was held between the future German empires that is Prussia and France lasted from 1870 to 1871. This war concluded with a humiliating defeat for France. It not only lost its prime regions of Lorraine and Alsace, but it was also forced to pay a huge indemnity to Prussia. This war eventually led to the development of a very powerful German Empire with a tremendous industrial and military potential which was sufficient enough to further disrupt the European power balance on one hand and widespread resentment and desire for revenge of French on the other hand.
The German foreign policy became more hostile after the accession of Wilhelm II to the German throne in 1888. The newly formed German Emperor immediately dismissed the skillful Otto Von Bismarck as the Chancellor. Not only this, he also declined the renewal of Reinsurance Treaty with Russia that kept fragile peace between Austria-Hungary and Russia and maintained France in isolation. This way Wilhelm II created an alliance in between Russia and France.
The rivalry between Russo and Japanese over the Korea and Manchuria reached its peak with the resulting Russo-Japanese War in 1904-1905. The war concluded as a major blow for the Russians by the Japanese who lost their entire Pacific and Baltic fleet. This defeat also provoked a very serious political crisis which subsequently led to the Russian Revolution of 1905.
The Moroccan Crisis had brought the European powers on the verge of war. Germans were the main face behind these crises with the target of creating tensions between the Britain and France alliance. However, it resulted into the opposite. Instead of transforming Britain and getting it close to the Central Powers, these crises further reinforced the Entente Cordiale and resulted into increased hostility of the British towards Germany.
It was in 1908 that Austria-Hungary planned to annex Herzegovina and Bosnia, which was the integral part of the Ottoman Empire. This annexation was very bitterly opposed by Serbia, which was very closely related to the province both geographically and ethically. Serbia at that time was supported by the Tsarist government and the crisis persisted into 1909. Russia somehow failed to win over a firm support from Britain or France, whereas Vinna enjoyed full support from Germany and accepted the full annexation of the province. Serbia was then forced to back out resulting into the end of crisis. But these crises permanently damaged the relationships between Russia and Serbia and between Austria-Hungry.
The Italo-Turkish war that took place between 1911 and 1912 did not disrupt the European peace. But the Turkish defeat exposed the weakness of the Ottoman army and also revealed the disagreement between the European powers about the fate of the decaying Ottoman Empire. The war between the Ottoman Empire and the Kingdom of Italy turned out to be an incentive for the Balkan League.
A group of conspirators belonging to Mlada Bosna (the revolutionary movement) carried out the assassination of the Austro-Hungarian heir presumptive, Archduke Franz Ferdinand and his wife on their visit to Sarajevo on 28th June, 1914. This event triggered the subsequent course of events that directly led to the outbreak of the Great World War I, but it did not cause it.