World War I, also known as the Great War, lasted from 1914 to 1918 and was one of the most devastating conflicts in human history. The main causes of this war can be divided into several categories: nationalism, alliances, imperialism, and militarism. Nationalism was a strong driving force before the war, especially in Europe. This can be seen in the increasing national aspirations of many countries, including Serbia, which sought to control the Slavic population in the Balkans. Tensions escalated following the assassination of Archduke Franz Ferdinand of Austria on 28 June 1914 by Gavrilo Princip, a Serbian nationalist. This assassination set off a series of events that ultimately led to the declaration of war between the major European powers. Alliances also play an important role in increasing conflict. Europe was divided into two large blocs: the Triple Alliance (Germany, Austria-Hungary, and Italy) and the Triple Entente (France, Russia, and England). When one country becomes involved in a conflict, other countries in the alliance feel compelled to join in, turning local skirmishes into large-scale wars. Imperialism was also an important factor, where European countries competed to control colonies in Asia and Africa. Competition for natural resources and new markets created tensions, especially between England and Germany. This conflict exacerbated instability in Europe, creating an atmosphere conducive to the outbreak of war. Militarism, or the strengthening of the armed forces, also adds to tensions. The major powers of Europe expanded their armed forces and developed military doctrines. This creates an atmosphere where war is considered an acceptable solution to resolve conflicts. The impact of World War I was broad and profound. Politically, the war resulted in the collapse of several large empires, such as the Austro-Hungarian Empire, the Ottoman Empire, and the German Empire. The formation of new states in Central and Eastern Europe, as well as changes to the political map of Europe, were also direct results of the war. Socially, World War I brought major changes in the structure of society. Many countries began to pave the way for women’s voting rights in exchange for their contributions on the battlefield. The psychological and physical trauma resulting from the war also created a generation known as the “Lost Generation.” The world economy was also hit by war. Many countries experience severe inflation and high national debt. The war caused destruction of infrastructure and affected international trade, creating the conditions that prompted the Great Depression in the 1930s. World War I also accelerated the emergence of new ideologies, such as communism and fascism, which would shape global political dynamics in the 20th century. The legacy of this conflict continues to influence international relations and the disputes that have emerged in its wake.