Our primary task as Christians is not to promote peace. We are to promote the Truth and be witnesses of Jesus Christ to a lost and dying world.
Jesus said, "Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword. For I have come to turn a man against his father, a daughter against her mother, a daughterinlaw against her motherinlaw" (Matt. 10:34,35).
We are at war with sin, Satan and worldliness:
"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" (Ephesians 6:12).
But we are waging a warfare that is different from this world's warfare:
"For though we live in the world, we do not wage war as the world does. The weapons we fight with are not the weapons of the world. On the contrary, they have divine power to demolish strongholds. We demolish arguments and every pretension that sets itself up against the knowledge of God, and we take captive every thought to make it obedient to Christ" (II Cor. 10:3-5).
However, sometimes the battles we fight take us into various aspects of this world (we are in the world but not of it). We need godly Christians serving in our military and our law enforcement departments. God uses us as His instruments in many different ways.
David was a man after God's own heart and he was a warrior. God used him to bring justice and judgment on the pagan nations that surrounded and infiltrated Israel. Jesus is the same God with whom David walked.
Sometimes war is necessary to bring about justice and peace (albeit temporary). No peace is permanent until the Prince of Peace defeats the unbelieving nations and sets up His Kingdom. But His perfect and permanent peace will be preceded by war to defeat those nations.
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"Be selfcontrolled and alert. Your enemy the devil prowls around like a roaring lion looking for someone to devour. Resist him, standing firm in the faith, because you know that your brothers throughout the world are undergoing the same kind of sufferings" (I Peter 5:8,9).
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