What were the main causes of World War I?

The assassination of Archduke Franz Ferdinand in Sarajevo in 1914 was indeed the immediate trigger for World War I, but the deeper causes of the conflict were rooted in a complex web of political, social, and economic factors that had been building over decades. One major cause was the system of alliances between the great powers of Europe. Countries formed defensive military agreements—such as the Triple Alliance (Germany, Austria-Hungary, Italy) and the Triple Entente (France, Russia, Britain)—which meant that any localized conflict risked escalating into a wider war. This alliance system created a climate of suspicion and competition, where nations felt compelled to support their allies aggressively. Nationalism was another powerful force. Many ethnic groups sought independence or greater autonomy, especially within multi-ethnic empires like Austria-Hungary and the Ottoman Empire. Intense national pride and rivalries often led to hostility between nations. For example, Slavic nationalism in the Balkans, supported by Serbia and Russia, threatened Austria-Hungary’s stability, increasing tensions in the region. Militarism and the arms race further heightened the risk of war. European powers invested heavily in expanding and modernizing their armies and navies, creating a culture that glorified military strength and readiness. This buildup made countries more willing to resort to force to resolve disputes. Additionally, imperial rivalries over colonies and global influence created friction, particularly between Britain and Germany, further destabilizing international relations. In summary, World War I was caused by a combination of tangled alliances, rising nationalism, militarism, and imperial competition, all of which created a fragile peace that was shattered by the assassination in Sarajevo. These underlying factors meant that a regional conflict quickly escalated into a devastating global war.