Spiritual warfare consists of struggling against evil forces in our minds. The Bible is clear that this is not a battle which is fought on a physical plane at all, but rather a spiritual one:
Ephesians 6:12, "For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places."
Who are those principalities, powers, rulers or darkness and such? They all stem from Satan's kingdom, but since Satan is not omnipresent (can be everywhere at once), he works through a network or an army of demon spirits. When a person says, "The devil is on my trail!" it is highly unlikely that Satan himself is assigned to the job, but rather one of the troops in his army, which would be a demonic spirit.
Defensive spiritual warfare
There are two kinds of spiritual warfare, offensive and defensive. In defensive spiritual warfare, demonic spirits (under Satan's command) are launched what is known as fiery darts, as Ephesians 6:16 tells us:
"Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the wicked."
These fiery darts come in one of three forms; temptations, deceptions and accusations. I will briefly cover each of these in this teaching, but there are additional teachings available on this site that specifically address each one of these.
Spiritual warfare dart #1: Temptations
Satan couldn't freely play havoc on Eve's life because he had no rights to her, so what did he do? He went about trying to get her to give him those rights. He tempted her to sin because sin gives the devil a foothold in our lives. Ephesians 4 is telling us to put off our old sinful nature and in verse 27, it tells us that we can give the devil a foothold in our lives through sin:
"Neither give place to the devil."
The devil tempted Eve in the garden because he had no 'place' in Eve's life, but he wanted one! If Satan wants more legal grounds in our lives, you can expect some temptations to come your way. That's his way of getting you to fall and give him a place to operate. The moment we fail and sin, it is important to quickly turn from those sins and repent so that we can be forgiven and the legal ground removed.
Spiritual warfare dart #2: Deception
I have seen Satan beat up more Christians then I care to admit. Countless believers are living in defeat because they have been deceived. The enemy has deceived them and caused them to believe and live a lie. If we allow deception to take hold, strongholds can then be formed in our minds. Strongholds are incorrect thinking patterns based on falsehood. Demonic spirits love to use these strongholds to their advantage against a child of God. Strongholds have tremendous power to affect our feelings and emotions. Many blood-bought children of God Almighty feel guilt-ridden and worthless because they don't see themselves they way they ought to. Many Christians feel unloved and not good enough to be accepted by God because they see Him wrongly. Their perception of Him has been damaged and causes them to see Him as a distant and cruel taskmaster instead of a close loving Father who longs (deeply desires) to have an intimate loving relationship with them!
2 Corinthians 11:3, "But I fear, lest by any means, as the serpent beguiled (deceived) Eve through his subtlety, so your minds should be corrupted from the simplicity that is in Christ."
Spiritual warfare dart #3: Accusations
Satan is known to be the accuser of the brethren. Not the accuser of the sinners or the world, but the children of God. He could care less about badgering those who are in his kingdom, but he loves to pick on the children of God.
Revelations 12:10, "...the accuser of our brethren..."
He accuses us by reminding us of our past sins and failures. If we listen to his accusations against us, we will begin to mediate on our pasts and it isn't long before we begin to feel guilt-ridden and see ourselves as failures. Both of which has been dealt with on the cross! Has not the blood of Jesus washed away our sin? Then we ought not to be thinking about it anymore.
Satan loves to take a child of the Almighty God, who's been washed clean in the blood of Jesus and is without spot nor blemish, and make them feel dirty, worthless and see them self as a failure. If we pay attention to the devil's accusations, they too can form strongholds in our minds that need to be torn back down before we can experience freedom.
Offensive spiritual warfare
Then we have offensive spiritual warfare, which usually consists of tearing down strongholds that have been formed in our minds when we have taken the bait and accepted the deceptions and lies of the devil. Since strongholds are incorrect thinking patterns based on error, the correct weapon we are supposed to use to tear down such strongholds is through meditating on and applying the truth, which is found in the Word of God.
Ephesians 6 speaks of the weapons that we are to use in spiritual warfare, and in verse 17 we are told to take up the sword of the Spirit, the offensive piece of weaponry:
"...the sword of the Spirit, which is the word of God."
A sword is an offensive weapon meant to tear down and destroy the enemy. This is exactly what meditating on the truth in God's Word does to strongholds, it tears them down! Strongholds are built on error, and torn down through truth.
The devil tells you: "You're a failure! Look at your past!"
God's Word tells you: "What past? The blood of Jesus has washed it away!"
If you meditate on the error, you will begin to feel guilty and see yourself as a failure, but if you mediate on God's Word, you begin to feel clean and victorious!"
In a nutshell, spiritual warfare is a battle that goes on in our minds between error and truth. If we can know the truth and focus on it, while at the same time ignoring the error, we will be successful in spiritual warfare hands down!