Our greatest battlefield is our mind. The Word of God. Jesus Christ has fought and won the battle for us. He overcame the world, the flesh, the devil, death, and hell for us.
Every good soldier has battle gear.
Since our battles are not flesh and blood our instruments of warfare can not be made of natural materials. Shields of metal or wood would do little to protect us from the onslaught of fiery darts. The strongest metal is to weak to protect our minds from the perversions suggested to us from a dark world. Our gear must be of supernatural origin. We all reach the place in our lives when we have to accept or reject the simple gospel truths in God's Word.