World War I, which lasted from 1914 to 1918, was one of the most destructive conflicts in human history. The main causes of this war were rooted in a combination of political, economic and social factors. Among these causes, the alliance system, nationalism, imperialism and militarism stand out as the main drivers. The emergence of alliances such as the Triple Entente (France, Russia, England) and the Triple Alliance (Germany, Austria-Hungary, Italy) created significant tensions. When Archduke Franz Ferdinand of Austria was assassinated in 1914, these tensions escalated into a large-scale conflict. One of the main causes is nationalism. The European countries involved struggled to demonstrate their strength and superiority. For example, France wanted revenge for its defeat in the Franco-Prussian War of 1870. In addition, nationalist sentiment in the Balkans, colored by Serbia’s ambition to expand its territory, also fueled tensions. Imperialism also played an important role in exacerbating the conflict. Countries such as England and France competed for colonies in Africa and Asia, while Germany was hampered in its imperialist ambitions. Conflicts of interest in these colonial territories often led to diplomatic tensions. The impact of World War I was profound and far-reaching. First, millions of lives were lost, with around 10 million soldiers and 7 million civilians becoming victims. The involvement of almost all major countries caused serious infrastructure damage in Europe. Additionally, the economies of many countries were shaken, creating a prolonged financial crisis. Politically, this war sparked drastic changes. Established empires such as the Austro-Hungarian, German, and Ottoman Empires disintegrated, giving way to new states forming in Europe and the Middle East. The emergence of new states led to ethnic clashes and unstable boundaries, which contributed to future conflicts. World War I also changed the way we viewed war and diplomacy. The Treaty of Versailles signed in 1919 demanded heavy reparations from Germany and sparked deep frustration. This was one of the causal factors that led to the emergence of extreme ideologies such as fascism and communism, as well as World War II in 1939. The social impact was no less significant, with major changes in gender roles. Women who left home to work in factories and receive medical care during the war helped change society’s perception of gender and fueled the women’s rights movement. Communities were forced to adapt to life after the war, facing deep trauma and loss. Overall, World War I not only affected the generations involved, but also shaped geopolitical and social patterns that persist into the 21st century. Conflict, reshaping of borders, and societal shifts laid the groundwork for understanding contemporary global dynamics.