Whether we are aware of it or not, we are engaged in a great battle.
3 And another sign appeared in heaven: behold, a great red dragon, with seven heads and ten horns, and on his heads seven diadems. 4 His tail swept down a third of the stars of heaven and cast them to the earth. And the dragon stood before the woman who was about to give birth, so that when she bore her child he might devour it. […] 17 Then the dragon became furious with the woman and went off to make war on the rest of her offspring, on those who keep the commandments of God and hold to the testimony of Jesus.
REVELATION 12:3-4, 17 ESV
The nature of that battle is spiritual, not earthly.
10 Finally, be strong in the Lord and in the strength of his might. 11 Put on the whole armor of God, that you may be able to stand against the schemes of the devil. 12 For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. 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 firm. 14 Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness, 15 and, as shoes for your feet, having put on the readiness given by the gospel of peace. 16 In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one; 17 and take the helmet of salvation, and the sword of the Spirit, which is the word of God, 18 praying at all times in the Spirit, with all prayer and supplication. To that end, keep alert with all perseverance, making supplication for all the saints…
EPHESIANS 6:10-18 ESV
Therefore, the weapons we use against the enemy are also spiritual.
3 For though we walk in the flesh, we are not waging war according to the flesh. 4 For the weapons of our warfare are not of the flesh but have divine power to destroy strongholds. 5 We destroy arguments and every lofty opinion raised against the knowledge of God, and take every thought captive to obey Christ…
2 CORINTHIANS 10:3-5 ESV
But there is also a battle raging within ourselves.
21 So I find it to be a law that when I want to do right, evil lies close at hand. 22 For I delight in the law of God, in my inner being, 23 but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members.
ROMANS 7:21-23 ESV
However, God intends for us to be victorious.
24 And when they brought those kings out to Joshua, Joshua summoned all the men of Israel and said to the chiefs of the men of war who had gone with him, “Come near; put your feet on the necks of these kings.” Then they came near and put their feet on their necks. 25 And Joshua said to them, “Do not be afraid or dismayed; be strong and courageous. For thus the Lord will do to all your enemies against whom you fight.”
JOSHUA 10:24-25 ESV
…for the Lord your God is he who goes with you to fight for you against your enemies, to give you the victory.
DEUTERONOMY 20:4 ESV
But thanks be to God, who gives us the victory through our Lord Jesus Christ.
1 CORINTHIANS 15:57 ESV
Remember the voice of the Holy Spirit always speaks in the language of conviction…while the enemy speaks in the language of condemnation.