Why was World War 1 accidental but World War 2 planned?

ww1 was like a domino effect. it was accidental because of all the alliances the European countries made with each other. it was susposed to be a war between two countries because of the assasination of an Austrian prince. but because of all the alliances all those other countries were dragged in also. ww2 was planned because Germany was out for revenge and wanted to gain their power back.