1) The system of alliances:
- There was a web of alliances between the European countries, which meant that if one country went to war, its allies were obligated to join in.
- For example, Germany had alliances with Austria-Hungary and Italy, while Russia had alliances with France and Serbia.
- When Austria-Hungary declared war on Serbia in 1914, Russia mobilized its army in support of Serbia, which in turn led Germany to declare war on Russia and France.
2) Imperialism and nationalism:
- The European powers were competing for control of colonies and resources in Africa, Asia, and the Middle East.
- This competition created tensions between the countries and made them more likely to go to war.
- For example, Britain and France were rivals in North Africa, while Germany and Russia were rivals in the Balkans.
3) Militarism:
- The European countries had been building up their militaries in the years leading up to World War I.
- This arms race created a sense of insecurity and fear among the countries and made them more likely to go to war.
- For example, Germany had the largest and most powerful army in Europe, while Britain had the largest and most powerful navy.