- Nationalism: Europe in the early 20th century was characterized by intense nationalism, with countries competing for territory, status, and power. These nationalistic sentiments created tensions and rivalries between nations.
- Imperialism: The major European powers had colonies and overseas territories, and there was a competition for territorial expansion and resources. Imperial rivalries were particularly intense in Africa and the Balkans.
- Militarism: In the years leading up to the war, there was a significant arms race among the major European powers. Countries built up their military strength and prepared for the possibility of armed conflict.
- System of Alliances: A complex web of alliances entangled European nations and tied them together. Most notable were the Dual Alliance between Germany and Austria-Hungary and the Triple Entente of Britain, France, and Russia. If a war broke out between some allied nations, it would inevitably lead to the involvement of others and thus lead to conflict on a European scale.
- The Assassination of Archduke Franz Ferdinand: The immediate trigger for World War I was the assassination of Archduke Franz Ferdinand of Austria, the heir to the Austro-Hungarian throne, by a Serbian nationalist in Sarajevo (part of present-day Bosnia and Herzegovina) on June 28, 1914. This event escalated tensions between Austria-Hungary and Serbia and led to the chain of events that ultimately sparked the war.