It is very important to know that you have been given authority by Jesus to casr out demons. Some people look at Jude where Michael, The Archangel Angel and Satan are fighting over the Body of Moses and Michael calls in Jesus to defeat Satan.They forget this was before Calvary and also that we have actually been given by Jesus a written delegation in mark 16:17 which authorises us to remove demons and to destroy their work.So ignore what the Bible says about how angels fight. We are in a different situation to them and have a different delegation to them to deal with Satan and his workings.