"And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels, and prevailed not; neither was their place found any more in heaven. And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceive the whole world: he was cast out into the earth, and his angels were cast out with him." (Revelation 12:7-9)
Satan was cast out of heaven into the earth, where the battles are now fought in the minds of humans. Whether we like it or not, we are all involved in this war.
The place of the battle is the human mind, because that is where we choose between right or wrong. Right choices bring love, faith, health, and confidence - resulting in a happy, fulfilled life. Wrong choices wreak havoc with fear, stress, sickness, and confusion - leading to an unfulfilled life. In this spiritual war, we as humans are no match for Satan's spiritual attacks. We must fight this spiritual war with spiritual weapons. Let us go to God's word to access the Mind of Christ in order to recognize the enemy, and put on the impenetrable full Armor of God. We must defeat Satan in every situation, as we are Christian soldiers in His victorious army. The Mind of Christ brings the peace that passes all understanding.