Modern World War refers to global conflicts that marked major changes in world tactics, technology, and geopolitics. The need to understand this history requires us to explore two world wars in depth: World War I and World War II. World War I, which lasted from 1914 to 1918, occurred as a result of rivalry between the world’s great powers, including England, France, Germany and Austria-Hungary. This war was characterized by the use of advanced firearms, tanks, and chemical weapons, drastically changing the face of warfare. The battle in the trenches became a symbol of the cruelty of this war, where billions of troops were trapped in a hopeless situation. One of the factors causing World War I was a complex alliance system. The Triple Alliance between England, France, and Russia faced the Twin Triple Alliance of Germany, Austria-Hungary, and Italy. Tensions in the Balkans, especially after the assassination of Archduke Franz Ferdinand, triggered a series of events that brought the world into decline. After World War I, the 1919 Treaty of Versailles caused widespread discontent in Germany. Heavy reparation burdens and military restrictions only added to feelings of resentment and injustice. This weakness was exploited by Adolf Hitler, who attempted to restore Germany’s power and lead the world towards World War II, lasting from 1939 to 1945. World War II was marked by greater and more widespread atrocities. Involving most of the world’s countries, this conflict was characterized by totalitarian ideology, including Nazism, Fascism, and communism. The battles of Stalingrad and D-Day became strategic landmarks that determined the course of the conflict. War technology also progressed rapidly with the development of fighter aircraft, aircraft carriers and nuclear weapons. On the other hand, the Holocaust that occurred under the Nazi regime demonstrated the darkest humanitarian dimensions of this war, where six million Jews were systematically massacred. The end of World War II was marked by the use of atomic bombs on Hiroshima and Nagasaki, which not only ended the war but also ushered in the era of the Cold War and the emergence of dominance of the United States and the Soviet Union. The Modern World War changed the geopolitical map completely. The creation of the UN, an international organization aimed at preventing future conflict, reflects the world’s desire to prevent similar divisions. In addition, the formation of NATO and the Warsaw Pact marked the polarization of the world into two opposing ideological blocs. Technological innovations that emerged from the war, such as radar, computers, and the development of weapons of mass destruction, also influenced post-war global social and economic life. Societies remaining from the war must adapt to new realities, including changes in gender roles and human rights. In the Indonesian context, the impact of the Modern World War was also felt. Colonialism became one of the main issues, which triggered the national movement towards independence. Once again, global dynamics influenced the course of this nation’s history, leading to the proclamation of independence in 1945. Shifts in the post-war world brought new challenges such as the cold war, decolonization, and globalization. The continued confrontation between major powers in the 21st century shows that the lessons of the Modern World War are still relevant. Understanding the history of this conflict is important for building sustainable peace and maintaining international stability.