God is at war with the spirit being we know as the Devil, Satan, or Lucifer, who rebelled against Him, and then twisted the hearts of Adam and Eve to get them to disobey Him. Satan is the same one who has since wreaked havoc on mankind, stealing, killing, and destroying everything and everyone he can (John 10:10). As the antithesis of God, who is love, Satan is pure hate.
What God and the Devil are fighting over is people. Knowing that his doom is certain because of the finished work of Jesus Christ, the Devil’s goal is to hurt God as badly as he can. He does so by trying to keep people from hearing the truth of God’s Word about Jesus Christ and thus getting saved. If people get saved, he still does all he can to make their lives miserable and to kill them. This relentlessly cruel being, who disguises himself as an angel of light, is in reality a liar, a deceiver, a murderer, and the personification of evil. If you give him a millimeter, he will take a light year.
God and the Lord Jesus are the epitome of love, and they will one day bring peace on earth, but they know that the wicked stand in the way of peace, and must be dealt with. When it comes to the pure evil that Satan embodies, the only way to have peace is by war, including eventually destroying him and all his allies. In the battle between good and evil, on the side of good there is God and his armies, both angels and human. On the side of evil is the Devil, his demons, and the people who knowingly or unknowingly side with him. Although it will not always be this way, the background of the spiritual and physical universe we are living in today is conflict. That is why the Bible says that God is a warrior. “The LORD is a man of war” (Exod. 15:3, KJV).