The Apostle Paul warns a visible church in Ephesus about an invisible enemy of spiritual forces and he’s after us too.
Put it On
The Apostle Paul tells us in Ephesians 6:11-12 to “Put on the whole armor of God, that you may be able to stand against the schemes of the devil. For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places.” Notice he specifically says to “put on the whole armor” and not just part of it. Imagine going into war with part of your armor missing. That’s the first place the enemy will try to strike you so we must “take up the whole armor of God” (Eph 6:13a).
The Whole Armor
Think about how hard if you had to fight an invisible enemy, but that’s just what believers are in for. Paul said that “we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places” (Eph 6:12). It would certainly be a lot easier to face an enemy we can see, but since fallen angels and Satan are spirit, they’re not visible to us. This is the very reason we need God’s armor.
The Apostle Paul tells us we must “take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand firm” (Eph 6:13), but only after “having fastened on the belt of truth, and having put on the breastplate of righteousness” (Eph 6:14), and this breastplate of righteousness is our faith in Christ by Whom we’re reckoned as righteous (2 Cor 5:21). We certainly need all the armor of God we can get, but notice it’s up to us to “take up” the armor. God will not put it on for us. We must take the initiative because armor doesn’t put itself on. We have to be involved.
The belt of truth means you know the truth and that truth has set you free because of your relationship with Jesus Christ. Jesus said “I am the way, the truth, and the life. No one can come to the Father except through me” (John 14:6), meaning, “there is salvation in no one else, for there is no other name under heaven given among men by which we must be saved” (Acts 4:12). The breastplate protects the vital organs, is that of Jesus’ own righteousness protecting us, but don’t miss the point that Paul said we need to “put on the breastplate” just as he had told us twice before to “put on the whole armor of God,” including the belt of truth. Jesus said His Word is truth!
Shod With the Gospel
You cannot have the peace of God until you’ve first made peace with God. The Apostle Paul tells us that, “as shoes for your feet, having put on the readiness given by the gospel of peace” (Eph 6:15), indicating once more that we need to be involved to put these shows on. Perhaps Paul says that the “shoes for your feet” are the “gospel of peace,” because we who have trusted in Christ are at peace with God because of Christ (Rom 5:1), meaning there is no more condemnation (Rom 8:1). The gospel of peace is the gospel that removes the enmity of God against us by Christ’s atoning work.
Gospel of Peace
The “shoes for your feet” might not mean much to us but to Paul it meant a lot because the Roman soldiers had heavy leather shoes that sometimes had spikes in them, much like golf shoes do, but only longer. These spikes were intended to stabilize the soldier in rough terrain or while engaged in a battle. The shoes of the gospel are our standing firmly on the promises of God (John 3:16) and being at the ready to give to others the reason for the hope that is in us (1st Pet 3:15), and the gospel brings us peace because the condemnation is lifted and they are not at peace with God (Rom 5:1, 8:1). You cannot have the peace of God without having made peace with God through Christ.
Shield of Faith
When Paul wrote tells us to “take up the shield of faith, with which you can extinguish all the flaming darts of the evil one” (Eph 6:16), once more it’s up to us to “take up” this shield. The faith that saves is a shield for us against the Day of Judgment that is coming on all unbelievers, but this shield if to be used against the enemy, and without faith, we couldn’t possibly defend ourselves against all the flaming darts of the enemy.
Extinguishing the Darts
It is a fact that our shield of faith protects us after being saved by grace through faith (Eph 2:2-9), and this shield is special. It’s meant to extinguish the flaming darts of the evil one (Satan). These flaming darts would do much harm without a shield of faith.
Christians are commanded to “take the helmet of salvation, and the sword of the Spirit, which is the word of God.” This helmet covers the head to protect it from false teachings and keeps us grounded by the head-knowledge of our security in Christ. If you have been saved, then you have access to the only offensive piece of equipment in the armor and that is “the sword of the Spirit.” The sword of the Spirit, being the Word of God equips us to be able to resist the enemy just as Jesus did in resisting the Devil’s temptations. When tempted by Satan, Jesus used the sword of the Spirit or the Word of God and the Devil had no answer to that.
The helmet protects the head, which is where the knowledge of our salvation lives, and we’ve seen that the sword of the Spirit is the Word of God, the Bible. It’s the only offensive weapon among all the armor. Jesus used the Word of God as a weapon in rebuking the Devil who was taking Scripture out of context, so it’s a great idea to memorize Scripture for the times you’re tempted.
One of the things we can use to fight the enemy is not even a piece of equipment but prayer. Paul tells us that we are to be “praying at all times in the Spirit, with all prayer and supplication. To that end, keep alert with all perseverance, making supplication for all the saints” (Eph 6:18). To keep alert is to keep the enemy from sneaking up on us and when we are praying, we are connecting with the God Who can see what we don’t see and help us avoid the enemies ambushes, for he lies in wait, like hungry lion seeking someone to devour (1 Pet 5:8).
Paul makes an important conclusion after we’ve put on all the armor of God. He says we’re to be “praying at all times in the Spirit, with all prayer and supplication. To that end keep alert with all perseverance, making supplication for all the saints, and also for me, that words may be given to me in opening my mouth boldly to proclaim the mystery of the gospel,” so for Paul, the armor enabled him to boldly “proclaim the mystery of the gospel” (Eph 6:18-19). We too need the armor of God. It’s up to us to put it on, but if you’ve never trusted in Christ, you have no protection from the evil one. Put your trust in the Savior, while it’s still called today (2 Cor 6:2), or face God’s wrath on Judgment Day (Rev 20:12-15) with no more chance to repent.
Here is some related reading for you: Spiritual Attacks: Putting on the Armor of God 
Resource – Scripture quotations are from The Holy Bible, English Standard Version® (ESV®), Crossway Bibles. (2007). ESV: Study Bible: English standard version. Wheaton, Ill: Crossway Bibles. Used by permission. All rights reserved.