What caused World War I?

World War I, often called the Great War, was caused by a complex combination of political, military, and social factors that had been building up in Europe for decades. The immediate trigger was the assassination of Archduke Franz Ferdinand of Austria-Hungary on June 28, 1914, by a Serbian nationalist in Sarajevo. However, this event alone did not cause the war; it set off a chain reaction among the major powers, which were already deeply entangled in alliances and rivalries. Several underlying causes contributed to the outbreak of WWI. Nationalism was on the rise, with various ethnic groups seeking independence or dominance, particularly in the Balkans. Militarism had led to an arms race, especially between Germany and Britain, increasing tensions and the readiness for war. Additionally, a system of complex alliances divided Europe into two main blocs: the Triple Entente (France, Russia, and Britain) and the Triple Alliance (Germany, Austria-Hungary, and Italy). When Austria-Hungary declared war on Serbia, these alliances quickly escalated the conflict into a broader war. Imperial competition and economic rivalries also played significant roles, as European powers vied for colonies and resources around the world. The combination of these political alliances, nationalist fervor, military preparations, and imperial ambitions created a volatile environment. Once the crisis began in 1914, the mechanisms of alliance commitments and mobilization plans propelled the continent rapidly into full-scale war.