The Church of Christ is continually represented under the figure of an army; yet its Captain is the Prince of Peace; its object is the establishment of peace, and its soldiers are men of a peaceful disposition. The spirit of war is at the extremely opposite point to the spirit of the gospel.
Yet nevertheless, the church on earth has, and until the second advent must be, the church militant, the church armed, the church warring, the church conquering. And how is this?
It is in the very order of things that so it must be. Truth could not be truth in this world if it were not a warring thing, and we should at once suspect that it were not true if error were friends with it. The spotless purity of truth must always be at war with the blackness of heresy and lies.
No one puts it better than the prince of preachers himself, C.H. Spurgeon. Well in light of this war that we cannot escape, we need to be equipped for battle. Check this out:
Ephesians 6:10-18 (New International Version)
The Armor of God
10Finally, be strong in the Lord and in his mighty power. 11Put on the full armor of God so that you can take your stand against the devil’s schemes. 12For 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. 13Therefore put on the full armor of God, so that when the day of evil comes, you may be able to stand your ground, and after you have done everything, to stand. 14Stand firm then, with the belt of truth buckled around your waist, with the breastplate of righteousness in place, 15and with your feet fitted with the readiness that comes from the gospel of peace. 16In addition to all this, take up the shield of faith, with which you can extinguish all the flaming arrows of the evil one. 17Take the helmet of salvation and the sword of the Spirit, which is the word of God. 18And pray in the Spirit on all occasions with all kinds of prayers and requests. With this in mind, be alert and always keep on praying for all the saints.