What triggered World War I?

World War I was triggered by a complex combination of political, military, and social factors that had been building up over decades in Europe. The immediate catalyst, however, was the assassination of Archduke Franz Ferdinand of Austria-Hungary on June 28, 1914, by a Serbian nationalist in Sarajevo. This event set off a chain reaction among the major powers due to a web of alliances, rivalries, and militarization. Beyond the assassination, several underlying causes contributed to the outbreak of the war. These include: 1. **Militarism:** European nations were engaged in an arms race, expanding their armies and navies, which created a tense environment where many believed war was inevitable or even desirable for national glory. 2. **Alliances:** Complex alliances divided Europe into two main camps—the Triple Entente (France, Russia, Britain) and the Triple Alliance (Germany, Austria-Hungary, Italy). These alliances meant that a conflict involving one country could quickly involve others. 3. **Imperialism:** Competition for colonies and global influence heightened tensions between the great powers, especially between Britain, France, and Germany. 4. **Nationalism:** Intense national pride and ethnic tensions, particularly in the Balkans, fueled conflicts. Slavic nationalism in the Balkans threatened the stability of Austria-Hungary, contributing to the assassination. When Austria-Hungary issued an ultimatum to Serbia after the assassination, Serbia’s partial rejection led Austria-Hungary to declare war. Russia mobilized to defend Serbia, Germany declared war on Russia and its ally France, and soon Britain entered the war, turning a regional conflict into a full-scale world war. In summary, while the assassination of Archduke Franz Ferdinand was the immediate trigger, World War I’s outbreak was the result of deep-rooted militarism, alliance systems, imperial competition, and nationalism that created a fragile and volatile environment in early 20th-century Europe.