The First World War, which lasted from 1914 to 1918, was one of the bloodiest conflicts in human history. The causes are very complex, involving various interrelated political, economic and social factors. One of the main causes of the First World War was the alliance system that formed in Europe. After the Balkan Crisis, two major blocs formed: the Allies, consisting of Britain, France, Russia, and later Italy, and the Central Powers, led by Germany, Austria-Hungary, and the Ottoman Empire. Tensions between these two alliances created an unstable atmosphere in Europe. The nationalism factor also plays a big role. Large countries such as Germany and France are trying to show their dominance. Within Austria-Hungary, there were stirrings of nationalism among ethnic Slavs seeking independence. The assassination of Archduke Franz Ferdinand on June 28, 1914 by Serbian nationalist Gavrilo Princip was the immediate trigger that sparked a large-scale conflict. The impact of the First World War was far-reaching. In the social aspect, millions of people were killed and injured, devastating young generations in many countries. The social and economic dissatisfaction that emerged as a result of the war also led to a wave of revolutions, including the Bolshevik Revolution in Russia in 1917. From a political perspective, the war changed the map of Europe. The German Empire, Austria-Hungary, Ottoman Empire, and Russia collapsed, while new states emerged. The Treaty of Versailles in 1919 required Germany to pay large reparations and accept full responsibility for the war, leading to feelings of resentment and discontent that contributed to the Second World War. Economically, the war caused severe infrastructure damage and economic crises in many countries. Many countries took on huge debts to finance the war, which worsened post-war economic conditions. Rising prices and high inflation haunt communities throughout Europe. The First World War also brought changes in military technology. Weapons such as tanks, machine guns, and airplanes were first used effectively, changing the way war was fought. Additionally, social behavior is changing; with many men fighting, women began to enter the workforce and became more active in fighting for their rights. In a global context, the First World War accelerated the emergence of the United States as a world power. After entering the war in 1917 and contributing greatly to the Allied victory, the US began to play a dominant role on the international stage. Overall, the First World War not only destroyed many countries and brought about fundamental changes in social, economic, and political structures, but also shaped the modern world as we know it today. This war taught the importance of diplomacy and finding peaceful solutions in resolving conflicts.