“Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword.” – Lord Jesus Christ (Matthew 10:34)
The ‘Sword’ of the Spirit is His Word (for offense).
“Take the helmet of salvation and the sword of the Spirit, which is the word of God.” (Ephesians 6:17)
It’s for an offense because Sword is a Weapon but we don’t fight with ‘flesh and blood’ with swords (or weapons) of this world as this verse reveals:
“The weapons we fight with are not the weapons of the flesh. On the contrary, they have divine power to demolish strongholds.” (2 Corinthians 10:4)
Thus, there is “no” such thing as a ‘Christian army’ ordained by God on this earth which uses ‘swords/weapons of this world’ and wages war against their ‘fellow man’ (or ‘flesh and blood’) under the New Testament Age:.
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The Battle is in the spirit realm in the heavenly places:
“because we have not the wrestling with blood and flesh, but with the principalities, with the authorities, with the world-rulers of the darkness of this age, with the spiritual things of the evil in the heavenly places;” (Ephesians 6:12)
In short, the battle is in the ‘heavens’ (spirit realm).