Nothing is said in the Bible about the devil having any heart. Jesus told us what we need to know about him; that he was a murderer from the beginning, that there is no truth in him, that lies are his native language, that he is a liar and the father of lies - John 8:44. The Bible further adds that Jesus came to destroy him who holds the power of death - the devil - and that Jesus came to free those who all their lives were held in slavery by their fear of death - Hebrews 2:14-15.
I would say from that, that "heartless" is too mild a description for Satan. But the heart of Jesus for sinners is amazing.
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.