By 1914, Britain, France, Russia, Germany, Austria-Hungary and Italy had built up large stockpiles of weapons and armies. The arms race caused tension between the countries and made war more likely.
2. Imperialism
The European powers competed for control of colonies in Africa, Asia and the Middle East. This competition for resources and land caused tension between the European powers and increased the risk of war.
3. Nationalism
Nationalism was a powerful force in Europe in the late 19th and early 20th centuries. Nationalists believed that their nation was superior to others and should be dominant. Nationalism caused tension between the European powers and made war more likely.
4. Secret alliances
The European powers signed a series of secret alliances in the years leading up to World War I. These alliances meant that if one country went to war, its allies would have to help. The secret alliances increased tension between the European powers and made war more likely.
5. The Assassination of Archduke Franz Ferdinand
The assassination of Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, sparked a chain of events that led to World War I. The assassination caused Austria-Hungary to declare war on Serbia, Russia to mobilize its army in support of Serbia, and Germany to declare war on Russia and France. Within days, most of Europe was at war.