“And I beheld, and, lo, in the midst of the throne and of the four beasts, and in the midst of the elders, stood a Lamb as it had been slain, having seven horns and seven eyes, which are the seven spirits of God sent forth into all the earth” (Rev. 5:6)
"You will understand a great mystery when you see that in the book of Revelation we are shown two sets of spirits which are sent forth into the same areas and seek to control the same territory — the “seven spirits of God” and the “three spirits of devils”! Right here lies the cause of the great battle within! The seven spirits of God signify the fullness of the spirit of the Lord raised up within God’s people. This seven-fold spirit is raised up to subdue, reconcile, and redeem the whole man — spirit, soul, and body. Thus we read that the seven spirits are “sent forth into all the earth” — truly into all the earth that we are, as well as into all the earth-realm where the Lord’s people dwell!"
Much more in the link:
"“In this spiritual battle, as in every other, the decisive part of the engagement is not public and ostentatious; it is in secret. Long before the armies clash in the open field, there has been a conflict in the general’s office, where pro met con, and the determinations were reached that controlled each movement of the outward war. Even in law, ‘Cases are won in chambers.’ So, in the achievement of divine nature and spiritual character there is a hidden battlefield on which the decisive conflicts of the kingdom of God are waged. Behind the Master’s public ministry, through which He moved with such amazing steadfastness, not to be deflected by bribes, nor halted by fear of man or devil, nor discouraged by weariness, lay the battles in the wilderness where He fought out in fasting and prayer the controlling principles of His life. Behind His patience in Pilate’s Court, and His fidelity on Calvary, lay the battle in Gethsemane, where the whole problem was fought through and the issue settled before the face of God. All public consequences go back to secret conflicts. Napoleon sat for hours in silent thought before he ordered the Russian Campaign. Washington, praying at Valley Forge, was settling questions on which the independence of his country hung. We are deceived by the garish stage-settings of big scenes in history. The really great scenes are rarely evident. The decisive battles of the world are hidden, and all the outward conflicts are but the echo and Reverberation of that more real and inward war."