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Robert Plummer and John Mark Terry have edited a new book entitled Paul’s Missionary Methods: In His Time and Ours (IVP Academic, 2012), building upon Roland Allen’s classic Missionary Methods: Saint Paul’s or Ours? from a century ago.

IVP has given me permission to post the entire chapter of Craig Keener’s chapter, “Paul and Spiritual Warfare” (PDF)—taken from Paul’s Missionary Methods edited by Robert L. Plummer and John Mark Terry. Copyright(c) 2012 by Robert L. Plummer and John Mark Terry. Used by permission of InterVarsity Press, P.O. Box 1400, Downers Grove  IL  60515-1426.

What follows is an excerpt of his helpful discussion on “the armor of God”:

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By comparing the lists in 1 Thessalonians 5:8 and Ephesians 6:14-17, we see that elements of the believer’s armor can prove interchangeable from one letter to another. That is, Paul draws on the particular items in the familiar Roman soldier’s equipment not to pair spiritual concepts with these items in a one to one correspondence, but to illustrate that we need to be spiritually equipped. Salvation or the hope of salvation is a helmet in both cases, but Paul has the breastplate of faith and love in one case, with a breastplate of righteousness and shield of faith in the other.

We should note that his images of spiritual warfare do not involve special formulas or secret techniques, but salvation, faith, love, righteousness and so on. Without having to rule out the “mystical” elements that some see in spiritual warfare at times (as in 2 Kings 6:17), Paul’s images of spiritual warfare tend to be more practical than some imagine. Most involve protective armor, and we are protected by our right relationship with God and one another.

As is also often pointed out, God’s warriors, like Roman soldiers, have protection only for the front and not the back. Soldiers who discarded their shields and fled made easy targets for pursuing enemies; Roman soldiers who marched side by side, advancing on the enemy, were considered virtually invincible.

Whereas soldiers wore some pieces of armor in other circumstances, they normally donned the helmet and breastplate only for battle. The armor depicted here, therefore, involves a spiritual warrior directly engaged in spiritual war, with the assumption that this is the believer’s normal state. . . .

What we can say for certain in Paul’s context is that we dare not wage our battle in our own strength, but by depending on God (Eph 6:10). Western Christians have grown accustomed to depending on economic resources, technology, information and everything else but God; the way to advance the kingdom, however, is by humble recognition that God does the most important work and deserves the real credit.


Because the first piece of armor mentioned guards the waist or loins (Eph 6:14), it refers to a “belt” or “girdle.” It may thus evoke the Roman soldier’s leather apron beneath the armor or the metal belt that guarded his lower abdomen. God’s warrior is protected partly by truth, which in the context of other virtues mentioned here may include integrity (cf. Eph 4:15, 25). For Paul, however, including in Ephesians, “truth” involves particularly the truth of the gospel, recognizing and living in the reality of God’s claims as opposed to the world’s falsehood (see Eph 1:13; 4:21, 24-25; 5:9; cf. Rom 1:18-19). Believers must live and speak consistently with God’s reality.


Paul next mentions the “breastplate” (Eph 6:14), meant to protect the chest and usually made of leather with metal over it. God himself wears “righteousness as a breastplate” in Isaiah 59:17, so he can enact justice and righteousness in a world that has abandoned it (Is 59:14-16). Part of God’s mission into which he has invited us as agents is to work for righteousness and justice, for God’s honor and the right treatment of people made in his image. Given Paul’s usual usage, however (including in Eph 4:24; 5:9), this “righteousness” is also part of the new standing and character God has given us in Christ. Only those with this status and heart before God will be pure agents of his righteousness in the world.


Soldiers also would wear sandals or half boots (Eph 6:15); this was necessary preparation for battle, so that one could advance against the enemy without needing to be distracted by what one might step on. Paul applies the image to “the gospel [good news] of peace,” clearly alluding to Isaiah 52:7, where heralds bring good news of divine deliverance and restoration for God’s people. Readiness to carry the gospel is necessary for God’s warriors to advance and, as we shall see, prepares us for the one offensive weapon that Paul will include: the gospel message (Eph 6:17).


Roman soldiers used rectangular shields about four feet high, covered with leather. Because such shields could be vulnerable to flaming arrows, soldiers could wet their shields before battles where such projectiles were expected. As the soldiers marched together in formation, the front row’s shields covering their front and the second row’s lifted shields guarding both rows from above, they were considered virtually invulnerable to projectiles that individuals hurled against them. Greeks and Romans sometimes thought of sexual temptation in terms of fire or wounds, but the meaning is undoubtedly broader than that; Scripture already used arrows as a metaphor for attacks from the wicked, including slander (Ps 11:2; 57:4; 58:6-7; 64:3; cf. 120:2-4; Prov 25:18). Given the normal case of the Roman soldier, however, Paul might assume something about our defense that we sometimes neglect: we dare not break ranks. We must march together, protecting one another.


The threat for Paul is not human, as for Roman armies, but “the evil one.” While Satan is powerful, however, Paul declares that the shield of faith is sufficient to put out the fire on his arrows. Believers should not become fearful of Satan’s attacks, but stand firm in faith. When readers think of “faith” today, because of the past two centuries of trends in philosophy we often think of a subjective feeling or of a mental ability to extinguish all doubt, both of which approaches put the focus on the believer’s effort. In Jesus’ teaching, however, the question is not how much faith one has (a mustard seed is enough), but in whom one has faith. In Paul’s letters, Jesus and God the Father are the proper objects of faith. This is not a leap into the dark, as some generalized attitude of belief would be; this is a deliberate step into the light of God’s reality. The protection afforded by faith comes not when we trust our faith, but when we trust God who is absolutely trustworthy and able to protect us.


Roman soldiers wore for battle bronze (or iron) helmets with long cheek pieces (Eph 6:17). The specific phrase, “helmet of salvation,” echoes Isaiah 59:17, as in Ephesians 6:14. In the immediate context in Isaiah, this helmet referred to God acting to deliver the oppressed from the wicked (Is 59:15-16), but in the larger context of Isaiah the theme of salvation included God delivering his people and all who would turn to him among the nations (e.g., Is 46:13; 49:6; 51:5-8). The message of salvation and God’s reign is also called “good news of peace” (Is 52:7; see also Eph 6:15). That context might suggest that we participate in bringing God’s message of salvation; more directly, given Paul’s usage in 1 Thessalonians 5:8, Paul means that we are protected by means of God’s salvation.


The list climaxes, however, with the only offensive weapon in the soldier’s equipment that Paul will list (Eph 6:17). This limitation is not because Roman soldiers carried only one weapon; in fact they carried more, a pike or lance (or two) as well as their sword and dagger. For believers, however, there is only one weapon—God’s message—and it is logical that Paul chooses the image of the sword over the lance. The front row of an advancing legion carried heavy pikes that deterred attackers and could be thrust into them at fairly close range. Once close battle ensued, however, the heavy pikes became less practical than swords. (The sword here was the gladius, roughly 20-24 inches in length.) Paul envisions hand-to-hand combat, spiritual warfare not from afar at this point but at close range.

Paul declares that this one offensive weapon is the “sword of the Spirit, which is the word of God.” While God’s word includes Scripture (which Jesus deployed against Satan at his temptation), Paul usually uses this phrase especially for the gospel (e.g., the same term in Rom 10:8, 17; the same idea in Eph 1:13). Every other piece of equipment Paul mentions protects us; the one piece that enables us to take back ground taken by the devil is the gospel—evangelism. Too often the church lives off the benefits of past revivals, waging a merely defensive battle as the world surrounds and constricts the church. The most strategic means God has provided us of reversing the direction of influence is for us to bring the good news of peace and salvation to the world, through evangelism. Evangelism is the one element of spiritual warfare that takes back Satan’s possessions. Without it, spiritual warfare is incomplete. Likewise, we are kept safe by truth, righteousness and salvation.


Heralds of peace, bearing the sword of the Spirit, will not always be well received. People in antiquity understood that heralds were granted diplomatic immunity, and any mistreatment of an ambassador signaled an act of war against the sender. Paul, however, is “an ambassador in chains” (Eph 6:20). Rome’s earthly empire was not willing to submit to God’s greater kingdom. Yet past earthly empires, including Rome, now lie in the dust, and God’s kingdom spreads, as promised, among all peoples. Jesus will return, and God’s kingdom will prevail. In the meantime, it often spreads, not through conquest, but through its agents’ suffering, as in Paul’s case.

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5 thoughts on “Heralds of Peace Wielding the Sword of the Spirit”

  1. Thanks for linking to the free chapter, Justin.

    Having just read ‘Understanding Spiritual Warfare: Four Views’ and been writing about it myself lately, I enjoyed Keener’s take on it. Especially appreciated was the emphasis on evangelism as spiritual warfare; precisely the idea I have been exploring.

  2. John says:

    I enjoyed the article but was very surprised he didn’t mention prayer, which plays a significant part in the passage (Eph 6:18-20).

  3. Richard says:

    I agree with John, I think the passage and message continues on with verse 18. That prayer is an important part of the Christian’s weapon (possibly more like a lance?).
    Many today seem to have forgotten how important earnest prayer is, especially when combined with regular fasting.

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Justin Taylor, PhD

Justin Taylor is executive vice president of book publishing and book publisher for Crossway and blogs at Between Two Worlds. You can follow him on Twitter.

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