The assassination of Archduke Franz Ferninand

Good stuff. While not directly a cause, I think the Balfour Declaration should have been mentioned too.

https://en.wikipedia.org/wiki/Balfour_Declaration

The issuance of the declaration had many long-lasting consequences. It galvanized popular support for Zionism, led to the creation of Mandatory Palestine, which later became Israel and the Palestinian territories, and was the origin of the ongoing Israeli Palestinian conflict, considered the world's most intractable conflict.