New Testament verses relating to warfare:

Ro 13:12 The night is far spent, the day is at hand. Therefore let us cast off the works of darkness, and let us put on the armor of light.
2Co 6:7 by the word of truth, by the power of God, by the armor of righteousness on the right hand and on the left,
2Co 10:3 For though we walk in the flesh, we do not war according to the flesh.
2Co 10:4 For the weapons of our warfare are not carnal but mighty in God for pulling down strongholds,
Eph 6:11 Put on the whole armor of God, that you may be able to stand against the wiles of the devil.
Eph 6:13 Therefore take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand.
Eph 6:14 Stand therefore, having girded your waist with truth, having put on the breastplate of righteousness,
Eph 6:16 above all, taking the shield of faith with which you will be able to quench all the fiery darts of the wicked one.
Eph 6:17 And take the helmet of salvation, and the sword of the Spirit, which is the word of God;
Php 2:25 Yet I considered it necessary to send to you Epaphroditus, my brother, fellow worker, and fellow soldier, but your messenger and the one who ministered to my need;
1Th 5:8 But let us who are of the day be sober, putting on the breastplate of faith and love, and as a helmet the hope of salvation.
1Ti 1:18 This charge I commit to you, son Timothy, according to the prophecies previously made concerning you, that by them you may wage the good warfare,
2Ti 2:3 You therefore must endure hardship as a good soldier of Jesus Christ.
2Ti 2:4 No one engaged in warfare entangles himself with the affairs of this life, that he may please him who enlisted him as a soldier.
Phm 1:2 to the beloved Apphia, Archippus our fellow soldier, and to the church in your house:
Heb 4:12 For the word of God is living and powerful, and sharper than any two-edged sword, piercing even to the division of soul and spirit, and of joints and marrow, and is a discerner of the thoughts and intents of the heart.
1Pe 2:11 Beloved, I beg you as sojourners and pilgrims, abstain from fleshly lusts which war against the soul,

(in context: Rom 13:12-Php 2:25, 1 Thess 5:8-1 Pet 2:11)

I just read this this morning, and it was rather interesting cuz recently, just this week especially, I am constantly having to remind myself we are in a war. And this war will not stop until Jesus returns to destroy this world and set up the new heavens and new earth. Until then, life is a battle and we are to be soldiers for God. I don't think many of us truly understand what it is to be a soldier, I know I certainly don't, but Paul uses the example many times. There are lots of references to being a soldier and being ready as a soldier. Ephesians 6 is one of the verses I have heard quoted and preached upon many time, and it is all about a soldier's preparation.

Spurgeon's Daily Devotion

"But all the Israelites went down to the Philistines, to sharpen every man his share, and his coulter, and his axe, and his mattock." — 1sa 13:20

We are engaged in a great war with the Philistines of evil. Every weapon within our reach must be used. Preaching, teaching, praying, giving, all must be brought into action, and talents which have been thought too mean for service, must now be employed. Coulter, and axe, and mattock, may all be useful in slaying Philistines; rough tools may deal hard blows, and killing need not be elegantly done, so long as it is done effectually. Each moment of time, in season or out of season; each fragment of ability, educated or untutored; each opportunity, favourable or unfavourable, must be used, for our foes are many and our force but slender.

Most of our tools want sharpening; we need quickness of perception, tact, energy, promptness, in a word, complete adaptation for the Lord's work. Practical common sense is a very scarce thing among the conductors of Christian enterprises. We might learn from our enemies if we would, and so make the Philistines sharpen our weapons. This morning let us note enough to sharpen our zeal during this day by the aid of the Holy Spirit. See the energy of the Papists, how they compass sea and land to make one proselyte, are they to monopolize all the earnestness? Mark the heathen devotees, what tortures they endure in the service of their idols! are they alone to exhibit patience and self-sacrifice? Observe the prince of darkness, how persevering in his endeavours, how unabashed in his attempts, how daring in his plans, how thoughtful in his plots, how energetic in all! The devils are united as one man in their infamous rebellion, while we believers in Jesus are divided in our service of God, and scarcely ever work with unanimity. O that from Satan's infernal industry we may learn to go about like good Samaritans, seeking whom we may bless!