There are a lot of different theories and historical facts under which circumstances the World War II could be prevented or avoided. discuss this.

use those website for reference:
http://www.debate.org/opinions/could-world-war-ii-have-been-avoided
https://www.quora.com/How-could-WWII-have-been-avoided
https://en.m.wikipedia.org/wiki/Johann_Georg_Elser