World War I (1914-1918) was a large-scale conflict that changed the political map of the world. The causes of this war are very complex, consisting of various interrelated factors. One of the main causes was the nationalism that swept Europe, where large countries such as Germany, France and England tried to show dominance. In addition, the alliance system established in the early 20th century also increased tensions. These alliances, such as the Triple Entente (France, Russia, and England) and the Triple Alliance (Germany, Austria-Hungary, and Italy), created an atmosphere in which the slightest conflict could turn into a major war. Imperialism is also an important cause. European countries tried to expand their power and territory through colonization. Competition for control of land in Africa and Asia intensified the conflict. Economic interconnections between countries also create tensions, with market and resource dominance often fueling intense competition. The assassination of Archduke Franz Ferdinand of Austria on June 28, 1914 by Gavrilo Princip, a Serbian nationalist, was the immediate trigger for the war. This assassination caused Austria-Hungary to issue an ultimatum to Serbia, which it could not fully fulfill, sparking war between the two. Within days, the alliances sprung into action, turning a bilateral conflict into a global war. In terms of impact, World War I caused enormous human losses with more than 16 million deaths. In addition, this war also triggered profound social changes. The role of women in society increased, because many men entered the battlefield. They are taking over jobs previously dominated by men, driving a change in perspective on gender in the world of work. Post-war global politics was also significantly affected. Dissatisfaction with the Treaty of Versailles in 1919, which required Germany to pay large reparations, created instability in Europe. This was one of the factors in the birth of Nazism and World War II. In addition, the growth of nationalist movements in European colonies was triggered by feelings of dissatisfaction with harsh colonial treatment. World War I also resulted in the creation of the League of Nations, an international organization aimed at preventing future conflict. Although the League of Nations failed to prevent World War II, the concepts of multilateral diplomacy and international cooperation began to be introduced in a global context. The legacy of this conflict can still be felt today, shaping many aspects of political, social and economic life in the modern world.