Nationalism, a strong sense of loyalty and devotion to one's nation, played a significant role in the outbreak of World War I. It led to WW1 in several ways:
1. Intense National Rivalries: The late 19th and early 20th centuries saw the rise of intense national rivalries among Europe's great powers, fueled by economic competition, colonial disputes, and a general scramble for power and influence. This created an atmosphere of mutual distrust and hostility that made war more likely.
2. Ethnic Tensions in Multi-National Empires: Nationalism also stirred up ethnic tensions within multi-national empires like Austria-Hungary and the Ottoman Empire. Various ethnic groups within these empires desired independence or greater autonomy, leading to internal conflicts that destabilized these empires and made them more prone to war.
3. The Assassination of Archduke Franz Ferdinand: The event that directly triggered WW1 was a product of nationalism - the assassination of Archduke Franz Ferdinand of Austria-Hungary by Gavrilo Princip, a Bosnian Serb nationalist who wanted Bosnia to be part of Serbia rather than Austria-Hungary.
4. Mobilization for War: Once war broke out, nationalism played a key role in mobilizing public support for the war effort. Governments used nationalist propaganda to rally their populations behind the war effort, portraying the war as a noble struggle for national survival or glory.
5. Alliance Systems: Nationalism also contributed to the formation of complex alliance systems among European nations before WW1 (e.g., Triple Entente between France, Russia, and Britain; Triple Alliance between Germany, Austria-Hungary, and Italy). These alliances were often based on shared national interests or common enemies. When one member of an alliance was attacked or threatened (as Austria-Hungary was after Ferdinand's assassination), its allies felt obligated to come to its defense out of national honor or self-interest, turning what might have been a local conflict into a world war.
In conclusion, nationalism was a major factor that led to WW1 by creating an environment of competition and hostility among nations, stirring up ethnic tensions within multi-national empires, triggering the war through an act of nationalist terrorism, mobilizing public support for the war, and contributing to the formation of alliance systems that turned a local conflict into a global one.