In Ephesians 6: 11, 15-17 Paul speaks about the armor of God, emphasizing the practical use of each piece of the equipment.  Paul is writing this passage telling the people to be ready for warfare against evil in the world, the powers of darkness, and spiritual wickedness in high places.
He speaks of the: Belt, Breastplate, Shoes, Shield, Helmet, and Sword.  Then he gives the spiritual equivalent for each piece of armor.

1. Belt of truth,  2. Breastplate of righteousness,  3. Shoes as the preparation of the gospel of peace,  4. Shield of faith,  5. Helmet of salvation  6. Sword of the Spirit, which is the word of God.  Paul was trying to give the people something they already knew about--Roman soldiers--as a comparison of how we should equip ourselves to face an evil world that would destroy our faith and cripple our witness.

I have a note in my Bible that I wrote years ago, probably from a sermon I heard, that God always fights with those six holy weapons (not destructive weapons) when dealing with Satan.  In our lives, God uses truth, righteousness, preparation, faith, salvation and His word to combat sin.

It is also interesting to note that of the six pieces of equipment, the first five are defensive.  Only the sixth piece of equipment, God's Word, is offensive. We have no offense against the false teachings around us in this misdirected world except the Word of God.

"Study to show yourself approved unto God, a workman that doesn't need to be ashamed, rightly dividing the Word of Truth."  ( II Timothy 2:15)  You can't fight a war effectively if you aren't prepared ahead of time.