World War I, which lasted from 1914 to 1918, was a historical event that changed the face of the world. The causes of this conflict are very complex, involving various political, social and economic factors. One of the main causes is the alliance system in Europe. Two large blocs, namely the Triple Alliance (consisting of France, Russia, and England) and the Central Empire (Germany, Austria-Hungary, and Italy), created tensions that led to war. The nationalism factor also contributed to the emergence of World War I. Countries in Europe, especially in the Balkans, wanted independence and self-recognition. The conflict culminated in the assassination of Archduke Franz Ferdinand of Austria in Sarajevo by Gavrilo Princip, a member of a Serbian nationalist group, on June 28 1914. This event triggered a chain reaction among the major countries in Europe. Apart from that, imperialism is also an important cause. Competition for colonies and resources made European countries increasingly aggressive. The newly unified Germany had ambitions to counterbalance British and French power in the world, leading to tensions between the great powers. The impact of World War I was far-reaching and profound. Millions of people were killed and injured, with total casualties reaching around 10 million soldiers and 7 million civilians. This humanitarian disaster affected the populations and economies of the countries involved. Infrastructure was destroyed in many places, especially in France and Belgium, which will take a long time to restore. World politics has changed drastically. Once powerful empires such as Austria-Hungary, Ottoman, and Russia collapsed, leaving a vacuum that was eventually filled by new states. The Treaty of Versailles, which ended the war, redrawn national borders and imposed heavy sanctions on Germany. This created a sense of discontent that ultimately contributed to the emergence of World War II. The world economy after the war experienced a recession. European countries struggled to pay war debts and rebuild their economies. In Germany, hyperinflation in the early 1920s created social and political instability, giving way to extremist ideologies. World War I also accelerated social change. Women began entering the workforce to replace men who went to war, paving the way for the women’s rights movement. The psychological consequences of war, known as “Shell Shock,” introduced new attention to mental health. World War I left a deep legacy, creating tensions that are still felt today. The idea between war and peace is an issue that continues to be discussed. With various factors triggering and destroying the lives of many people, the lessons of World War I remain relevant for future generations.