Respuesta :

the reasons were 1) imperialism: countries wanted their own empires. 2)nationalism: countries thought that their race was better than others.
3)militarism:countries wanted bigger armies than others [the navy, the air force...]
4)alliances: different counties signed treaties which included protection against enemies that threatened the country.
1) Militarism
2) Mutual offense alliances 
3) Imperialism