The war started mainly because of four aspects: Militarism, Alliances, Imperialism and Nationalism. This is because big armies become potential threats to other countries, other countries started forcing alliances in order to secure land.
The war started because of the assassination of Franz Ferdinand who was the future ruler of Austria-Hungary the killer’s name was Gavrillo Princip and that led to war between two countries a and over a period of time they brought in their allies to fight in a world wide battle
