world war one has been known as the worst war that had ever happened .....
why ??

Because at that time, mechanized warfare was available and it led to the most terrible thing, because everyone started using automobiles, airplanes and other mechanized military transportation to start bombing countries and send them grenades, fire, cannons and other things that can make the country to experience a sudden loss.

MAIN CAUSES OF WW1

M - militarism 

A - alliance 

N - nationalism 

I - imperialism 

A - assacination