What caused World War I?

World War I, which began in 1914, was caused by a complex mix of political, military, and social factors that had been building up in Europe for decades. The main causes are often summarized as militarism, alliances, imperialism, and nationalism—sometimes called the "MAIN" causes. 1. **Militarism:** European powers were engaged in an arms race, building up massive armies and navies. This created a tense environment where countries were prepared for war and believed military strength was essential to national prestige and security. 2. **Alliances:** Europe was divided into two major alliance systems—the Triple Entente (France, Russia, and Britain) and the Triple Alliance (Germany, Austria-Hungary, and Italy). These alliances meant that a conflict involving one country could quickly involve its allies, turning a small dispute into a large-scale war. 3. **Imperialism:** Competition for colonies and global dominance increased tensions between the great powers. Rivalries over territories in Africa, Asia, and elsewhere fueled distrust and conflict. 4. **Nationalism:** Intense pride and loyalty to one’s nation or ethnic group often led to conflicts, especially in multi-ethnic empires like Austria-Hungary. Nationalist movements sought independence or dominance, increasing instability. The immediate spark was the assassination of Archduke Franz Ferdinand of Austria-Hungary by a Serbian nationalist in June 1914. This event triggered a chain reaction of ultimatums, mobilizations, and declarations of war due to the existing alliances and tensions. In summary, World War I was caused by a combination of deep-rooted rivalries, military buildups, alliance commitments, and nationalist fervor, with the assassination of the Archduke acting as the catalyst that ignited the conflict.