Mohammad did it because in the 7th century thats what you did, someone got in your way, assassination was on the approved list of methods for dealing with it. The Byzantines did it all the time, Heraclius the Byzantine Emperor did it to his predecessor Phocus, Clovis was doing it in France, the Sassanians did it, life was cheap. So what else is new.
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.