Why war world one start?

Answer 1

World War 2 began on 1 September 1939 when German troops attacked Poland because Adolf Hitler wanted to control all of Europe and he started with Poland.

Answer 2

World War One started because of the assasination of Archduke Franz Ferdinand of Austria.

Answer 3

When the Germans began the invasion of Poland in 1939.

but, it is often debated because the Japanese were holding a campain in manchuria.