What were a few of the underlying reasons that world war 1 began?

1) Militarism

2) Mutual offense alliances

3) Imperialism

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.