In 1655, Puritan pastor William Gurnall began publishing The Christian in Complete Armour, addressing the “war between the saint and Satan […] so bloody a one, that the cruelest which was ever fought by men will be found but sport and child’s play” by comparison. This commentary on Ephesians 6:11-20 totals over 1,100 pages in the Banner of Truth edition; by contrast, Iain M. Duguid’s The Whole Armor of God: How Christ’s Victory Strengthens Us for Spiritual Warfare comes in at a less daunting 120. Though partly inspired by Gurnall, Duguid doesn’t aspire to his breadth. Rather, he offers an encouraging, pastorally rich guide that will be useful for settings like small groups or one-on-one discipleship, as well as for anyone who’s read Ephesians 6 and despaired at what they took for a spiritual to-do list. Adapted from his preaching over the course of 25 years, Duguid distills the meaning and application of each part of the “whole armor of God.”
He begins by looking at “three perspectives that orient us to the larger fight”: the scale of our spiritual need, the vastness of God’s provision (He has supplied that very same power which, per Ephesians 1:19-20, raised Christ from the dead), and the call to stand (10). Crucially, he points out that sanctification is not a question of simply “trying harder,” for as Heidelberg Catechism Q&A 114 tells us, even the holiest believer makes “only a small beginning of […] obedience” during this life. God’s sanctifying power works in Christians both in a once-for-all way and in an ongoing, progressive way. Even this latter sanctification, Duguid points out, is “ultimately no more under our control than God’s first work of regenerating us” (see Westminster Confession of Faith 16.3). The reason is that God wants us to learn our utter dependence upon Him—not to grow confident in our own strength. God empowers us to stand against sin and Satan, and He does that by equipping us with the armor that Christ Himself has worn on our behalf.
Duguid examines each piece of spiritual armor in turn, beginning with the belt of truth. Putting on this “belt” requires daily refilling our “leaky” hearts with the truth of the Scriptures, so that we are prepared to resist the lies of Satan. One of the strengths of the book is that Duguid uses his Old Testament expertise to show that Paul’s spiritual armor wasn’t new imagery, but originated chiefly in Isaiah. Here, Duguid explains that in Isaiah 11:5, the coming Messiah is described as wearing a belt of “faithfulness,” translated in the Greek Septuagint as aletheia, truth (33). It was this belt of truth that equipped Jesus to answer Satan’s temptations in the desert, and the same enables us to face our spiritual battles with a biblically saturated knowledge of God as our loving, forgiving Father.
After the “breastplate of [Christ’s] righteousness” and “shoes for your feet” (“gospel boots”!), Duguid takes up the “shield of faith.” This refers us not to our own faith, but to God, our refuge; faith being the means by which we cling to Him for protection in our struggles. Duguid argues that in order for our faith to function in this way, we must not only know that God is powerful, but that He is our friend, which we know not on the basis of fluctuating feelings, but on what His Word reveals to us. We deploy the shield of faith by reminding ourselves of the promises of His faithfulness, in other words—not of the strength of our faith.
The “helmet of salvation” comes directly from Isaiah 59:17’s description of the divine warrior. Duguid explains that throughout Isaiah, salvation is always closely linked to God’s righteousness, his promise-keeping faithfulness. This same biblically-grounded “settled hope” is our helmet, which Christ, whose hope in His Father never wavered, has already worn in our place. Such hope is eminently practical, protecting us against discouragement and despair much as a battle helmet protects a soldier against bullets (82). Such hope also gives us boldness in our pursuit of God’s call, whether that call looks obviously risky or merely “ordinary” by reminding us that no labor for Christ will ever be in vain, “even if the only visible fruit is a single human life—ours—growing in gratitude to the God who called us and sustains us by his grace” (85). We cultivate such hope by partaking of God’s appointed means of grace: for example, meditating on Scripture passages that stoke our appetite for heaven, and participating reflectively in the Lord’s Supper.
The “sword of the Spirit” is the Word of God—and in contrast to the others, which are primarily defensive in nature, it’s the only offensive weapon in our spiritual armor (91). As Duguid points out, we do not want to find ourselves in the position of learning to use our “sword” mid-battle. Rather, we should learn to put Scripture to work in small challenges so as to train ourselves for big ones, asking the Holy Spirit to be our teacher each time we open Scripture, and gaining from the insights of both godly contemporaries and sound historical interpreters. Per Isaiah 49:2 (“[The Lord] made my mouth like a sharp sword”), Jesus both wields and is Himself the Word of God (101).
In one of the most helpful brief treatments of prayer I’ve seen, Duguid closes with a discussion of “praying always,” which is “not so much another weapon […] as it is the means by which all of [the Christian’s] weaponry is kept effective under the control and guidance of God” (104). He acknowledges that prayer is often a struggle even for seasoned believers, because we think of it more as a technique that, if applied properly, will yield the proper results; not “the natural outworking of a life lived in utter dependence upon God” (105). As adopted children of God, though, we have His Spirit indwelling us and testifying within us; thus, we can know that God always delights to hear us. Our problem, then, isn’t a lack of technique: it’s an insufficient grasp of God as our loving heavenly Father and of the privileges we enjoy in Christ (108). Jesus’s High Priestly Prayer (John 17) is a wonderful passage to study in order to help these truths sink in. Of course we can also rest in the knowledge that Jesus is always praying for us; his perfect prayers covering the imperfections of our own.
What I appreciated most about The Whole Armor of God is the emphasis on the concreteness of faith. The point of Paul’s use of the Old Testament imagery is not just to be rhetorically memorable; it is meant to drive home that we must stand against real “cosmic powers over this present darkness” (Eph. 6:12). Therefore, we can’t just be vaguely or abstractly prepared; we have to be specifically equipped and trained to use the armor God gives us—as comfortably reliant on them as a warrior with weapons. The best news is that we can put our faith in a true Warrior who has worn this armor impeccably and effectually for us. As Duguid puts it, Christ’s armor “is not a pristine, clean outfit: it is already bloodied from his fight” at the cross (35).
Sarah White (MA, St. Louis University) is a writer living in Pittsburgh, Pennsylvania, with her husband, Kevin, and her Basset Hound, Basil.
 Joel R. Beeke and Randall J. Pederson, eds., Meet the Puritans: With a Guide to Modern Reprints (Grand Rapids, Michigan: Reformation Heritage Books, 2010), 306.