The First World War, which lasted from 1914 to 1918, was the first global conflict involving many major powers, known as the Allies and Central Powers. This conflict not only damaged political stability in Europe, but also had a major impact on the subsequent geopolitical map of the world. Through in-depth analysis, we can understand the main causes, course of the war, and its impact. One of the main causes of this conflict was the complex system of alliances among European countries. The involvement of countries such as Germany, Austria-Hungary, Britain, France, and Russia created tensions that spanned the entire continent. The assassination of Archduke Franz Ferdinand of Austria on 28 June 1914 by a Serbian nationalist, Gavrilo Princip, was the immediate trigger that sparked a series of declarations of war. During the war, warfare tactics and technology underwent major transformations. The use of automatic weapons, tanks, and aircraft changed the face of the battlefield. The battles at Verdun and the Somme became symbols of the long war and the heavy losses suffered by both sides. In these battles, millions of soldiers lost their lives, and many suffered lifelong injuries. This war also had an impact on civil society. The increasingly widespread colonization caused unrest in Africa and Asia, where many countries were forced to get involved directly or indirectly in this conflict. Nationalistic ideas began to emerge, and many colonies hoped to gain independence after seeing the instability of their colonial countries. On the economic side, the First World War changed production and consumption patterns globally. Countries were forced to divert their resources to support the war effort, leading to food crises in some regions. After the war ended, many countries faced huge debts and high inflation which caused dissatisfaction among citizens. Post-war, the Treaty of Versailles signed in 1919 became highly controversial. Germany, considered the main cause of the war, was burdened with heavy reparations that contributed to the country’s economic crisis in the late 1920s. This dissatisfaction created friction that sparked the emergence of extreme ideologies, including fascism and nationalism, which ultimately led to the Second World War. Analysis of the First World War shows that this conflict was more than just a war between countries. It reflects deep social, political, and economic changes. Lessons from the First World War are important to prevent the recurrence of similar conflicts in the future, encouraging the importance of diplomacy and international cooperation to create a more peaceful and stable world.