Our struggle is not against flesh and blood

Guido Reni‘s archangel Michael (in the Capuchin church of Santa Maria della Concezione, Rome, 1636) tramples Satan. 

A mosaic of the same painting decorates St. Michael’s Altar within St. Peter’s Basilica. 

For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.
Eph 6:12

Barnes' Notes on the Bible

For we wrestle - Greek, "The wrestling to us;" or, "There is not to us a wrestling with flesh and blood." There is undoubtedly here an allusion to the ancient games of Greece, a part of the exercises in which consisted in wrestling; see the notes on 1 Corinthians 9:25-27. The Greek word used here - πάλη palē - denotes a "wrestling;" and then a struggle, fight, combat. Here it refers to the struggle or combat which the Christian has to mainrain - the Christian warfare.  Not against flesh and blood - Not with people; see the notes on Galatians 1:16. The apostle does not mean to say that Christians had no enemies among men that opposed them, for they were exposed often to fiery persecution; nor that they had nothing to contend with in the carnal and corrupt propensities of their nature, which was true of them then as it is now; but that their main controversy was with the invisible spirits of wickedness that sought to destroy them. They were the source and origin of all their spiritual conflicts, and with them the warfare was to be maintained.  But against principalities - There can be no doubt whatever that the apostle alludes here to evil spirits. Like good angels, they were regarded as divided into ranks and orders, and were supposed to be under the control of one mighty leader; see the notes on Ephesians 1:21. It is probable that the allusion here is to the ranks and orders which they sustained before their fall, something like which they may still retain. The word "principalities" refers to principal rulers, or chieftains.  Powers - Those who had power, or to whom the name of "powers" was given. Milton represents Satan as addressing the fallen angels in similar language: "Thrones, dominations, princedoms, virtues, powers."  Against the rulers of the darkness of this world - The rulers that preside over the regions of ignorance and sin with which the earth abounds, compare notes on Ephesians 2:2. "Darkness" is an emblem of ignorance, misery, and sin; and no description could be more accurate than that of representing these malignant spirits as ruling over a dark world. The earth - dark, and wretched and ignorant, and sinful - is just such a dominion as they would choose, or as they would cause; and the degradation and woe of the pagan world are just such as foul and malignant spirits would delight in. It is a wide and a powerful empire. It has been consolidated by ages. It is sustained by all the authority of law; by all the omnipotence of the perverted religious principle; by all the reverence for antiquity; by all the power of selfish, corrupt, and base passions. No empire has been so extended, or has continued so long, as that empire of darkness; and nothing on earth is so difficult to destroy.  Yet the apostle says that it was on that kingdom they were to make war. Against that, the kingdom of the Redeemer was to be set up; and that was to be overcome by the spiritual weapons which he specifies. When he speaks of the Christian warfare here, he refers to the contest with the powers of this dark kingdom. He regards each and every Christian as a soldier to wage war on it in whatever way he could, and wherever he could attack it. The contest therefore was not primarily with people, or with the internal corrupt propensities of the soul; it was with this vast and dark kingdom that had been set up over mankind. I do not regard this passage, therefore, as having a primary reference to the struggle which a Christian maintains with his own corrupt propensities. It is a warfare on a large scale with the entire kingdom of darkness over the world. Yet in maintaining the warfare, the struggle will be with such portions of that kingdom as we come in contact with and will actually relate:  (1) to our own sinful propensities - which are a part of the kingdom of darkness; (2) with the evil passions of others - their pride, ambition, and spirit of revenge - which are also a part of that kingdom; (3) with the evil customs, laws, opinions, employments, pleasures of the world - which are also a part of that dark kingdom; (4) with error, superstition, false doctrine - which are also a part of that kingdom; and, (5) with the wickedness of the pagan world - the sins of benighted nations - also a part of that kingdom. Wherever we come in contact with evil - whether in our own hearts or elsewhere - there we are to make war.  Against spiritual wickedness - Margin, "or wicked spirits." Literally, "The spiritual things of wickedness;" but the allusion is undoubtedly to evil spirits, and to their influences on earth.  In high places - ἐν τοῖς ἐπουράνιοις - "in celestial or heavenly places." The same phrase occurs in Ephesians 1:3; Ephesians 2:6, where it is translated, "in heavenly places." The word (ἐπουράνιος epouranios) is used of those that dwell in heaven, Matthew 18:35; Philippians 2:10; of those who come from heaven, 1 Corinthians 15:48; Philippians 3:21; of the heavenly bodies, the sun, moon, and stars, 1 Corinthians 15:40. Then the neuter plural of the word is used to denote the heavens; and then the "lower" heavens, the sky, the air, represented as the seat of evil spirits; see the notes on Ephesians 2:2. This is the allusion here. The evil spirits are supposed to occupy the lofty regions of the air, and thence to exert a baleful influence on the affairs of man. What was the origin of this opinion it is not needful here to inquire. No one can "prove," however, that it is incorrect. It is against such spirits, and all their malignant influences, that Christians are called to contend. In whatever way their power is put forth - whether in the prevalence of vice and error; of superstition and magic arts; of infidelity, atheism, or antinomianism; of evil customs and laws; of pernicious fashions and opinions, or in the corruptions of our own hearts, we are to make war on all these forms of evil, and never to yield in the conflict.


Matthew Henry's Concise Commentary
6:10-18 Spiritual strength and courage are needed for our spiritual warfare and suffering. Those who would prove themselves to have true grace, must aim at all grace; and put on the whole armour of God, which he prepares and bestows. The Christian armour is made to be worn; and there is no putting off our armour till we have done our warfare, and finished our course. The combat is not against human enemies, nor against our own corrupt nature only; we have to do with an enemy who has a thousand ways of beguiling unstable souls. The devils assault us in the things that belong to our souls, and labour to deface the heavenly image in our hearts. We must resolve by God's grace, not to yield to Satan. Resist him, and he will flee. If we give way, he will get ground. If we distrust either our cause, or our Leader, or our armour, we give him advantage. The different parts of the armour of heavy-armed soldiers, who had to sustain the fiercest assaults of the enemy, are here described. There is none for the back; nothing to defend those who turn back in the Christian warfare. Truth, or sincerity, is the girdle. This girds on all the other pieces of our armour, and is first mentioned. There can be no religion without sincerity. The righteousness of Christ, imputed to us, is a breastplate against the arrows of Divine wrath. The righteousness of Christ implanted in us, fortifies the heart against the attacks of Satan. Resolution must be as greaves, or armour to our legs; and to stand their ground or to march forward in rugged paths, the feet must be shod with the preparation of the gospel of peace. Motives to obedience, amidst trials, must be drawn from a clear knowledge of the gospel. Faith is all in all in an hour of temptation. Faith, as relying on unseen objects, receiving Christ and the benefits of redemption, and so deriving grace from him, is like a shield, a defence every way.

The devil is the wicked one. Violent temptations, by which the soul is set on fire of hell, are darts Satan shoots at us. Also, hard thoughts of God, and as to ourselves. Faith applying the word of God and the grace of Christ, quenches the darts of temptation. Salvation must be our helmet. A good hope of salvation, a Scriptural expectation of victory, will purify the soul, and keep it from being defiled by Satan. To the Christian armed for defense in battle, the apostle recommends only one weapon of attack; but it is enough, the sword of the Spirit, which is the word of God. It subdues and mortifies evil desires and blasphemous thoughts as they rise within; and answers unbelief and error as they assault from without. A single text, well understood, and rightly applied, at once destroys a temptation or an objection, and subdues the most formidable adversary. Prayer must fasten all the other parts of our Christian armour.

There are other duties of religion, and of our stations in the world, but we must keep up times of prayer. Though set and solemn prayer may not be seasonable when other duties are to be done, yet short pious prayers darted out, always are so. We must use holy thoughts in our ordinary course. A vain heart will be vain in prayer. We must pray with all kinds of prayer, public, private, and secret; social and solitary; solemn and sudden: with all the parts of prayer; confession of sin, petition for mercy, and thanksgiving for favours received. And we must do it by the grace of God the Holy Spirit, in dependence on, and according to, his teaching. We must preserve in particular requests, notwithstanding discouragements. We must pray, not for ourselves only, but for all saints. Our enemies are mighty, and we are without strength, but our Redeemer is almighty, and in the power of his mighty we may overcome. Wherefore we must stir up ourselves. Have not we, when God has called, often neglected to answer? Let us think upon these things, and continue our prayers with patience.