There were angels who followed Satan in his rebellion against God. The Bible says one third of God's angels, followed Satan.(Rev 12:4) God cast Satan out of heaven (John 12:31) and Jesus saw him fall like lightening, (Luke 10:18), so his angels went with him - hence their title "fallen angels" which have become demons of course in Satan's kingdom of darkness. (See Ezekiel 28 11-19) - the King of Tyre is Satan.
So in response to your question there is absolutely no difference between the three categories you mentioned - they are all demons, evil spirits, wicked messengers of Satan Satan's cohorts are demons, or fallen angels or evil spirits - it's all the same thing because when the angels followed Satan they became fallen angels, evil spirits.
Demons are not fallen angels but are the past life energies of the dead brought up out of sheol (complete sleep) by those who break God's word and practice the occult. Because the living have power over the dead when these past life energies are brought up and they possess someone the possessed suffer because the dead are not able to repent and change they are unable to deal with present Life and also if they were evil and died evil and terrible deaths the possessed will experience the same kind of emotions they experienced at their death. Unless one repents they will curse their self and everyone else that listens to them.
There are no fallen angels the Devil was Cain the first murderer and liar in the bible and his angels are his offspring who prove who they are by murdering and lying. There have been a couple of the descendants of Cain referred to as the devil because before God there is no time and all seeds are one before Him. One of Cain's descendants was also a priest in the temple and he was the one who tempted Jesus.
Angels cannot temp anyone because they do not have flesh and do not know temptation. Satan which an angel of the LORD some times is used to test (not tempt) so he was sent by God to test Jesus in this flesh and for that reason he used a descendant of Cain the Devil I might add that an angel can be seen as evil by those who are doing evil but they are doing the work of God in detail.
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.