Causes

Nationalism, internal conflicts, and militarism all played a role in starting World War I.

The growth of nationalism in the nineteenth century had many serious results. Competition for colonies and trade increased. Europe’s great powers were soon divided into two alliances, the Triple Alliance and the Triple Entente. This period is called the armed peace.

Crises in the Balkans between 1908 and 1913 made many European nations angry with each other. They were willing to go to war to preserve the power of their national states.
Conscription, a military draft, was used by most Western nations before 1914. It caused the size of European armies to double between 1890 and 1914.
Militarism (aggressive preparation for war) was growing. Military leaders became more powerful