My theory is that between ROTJ and Epi VII is that Luke grew to powerful as a Jedi. Fearing that he might turn to the dark side, he goes into self exile like Yoda and Obi Wan did. No one knows where he is.
The events in Epi VII have made that Leia asks Han to search for Luke as the New Order is growing powerful and the Resistance can not defeat them without help from a powerful Jedi like Luke. I think that is the subplot about in the movie, hence the title, The Force Awakens, in this case, The Force is Luke. I think that Kylo Ren is Han & Leia's son, was taught about the Force by Luke but turned evil.
Maybe another reason why Luke is in exile. Rey could also be Leia & Han's daughter, but I like the idea that she is Luke's daughter (he may or may not know of her existance) and she is on Jakku to protect her idenidity (maybe sent there by Leia). ANd yes, I think that we see Luke in the teaser~trailer, with his robotic hand and with Artoo, but if he is in exile, why is Artoo with him?
You'll get to know what happened to him in Episode 8!
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.