If you want to know the enemy, memorize the Bible. Know the Bible, learn the Bible and the stories it contains, learn the theology of the Bible. Learn why God destroyed so many people in the Bible and what was at the root of that. Learn why God hates that so much. Memorize these things and know them. Jude says,
Nick BatzigI want to remind you, though you once knew this.They had forgotten the story about Israel. They had forgotten about the unfallen angels and they had forgotten about Sodom and Gomorrah. And so Jude is saying, remember these things because that is the first step in marking and knowing the enemy.1
5 Je veux vous rappeler, à vous qui savez fort bien toutes ces choses, que le Seigneur, après avoir sauvé le peuple et l'avoir tiré du pays d'Egypte, fit ensuite périr les incrédules;