Spiritual warfare and the finished work of Christ is a great subject.
'Get thee behind me Satan.' is a phrase an individual may utter all the time or one that they never utter at all. Perhaps that depends on what teachers they have had or books they have read. Is there a devil under every rock and misfortune or is it all people and events? Where is the battle and who are we resisting?
"And you, who were dead in your trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, by canceling the record of debt that stood against us with its legal demands. This he set aside, nailing it to the cross. He disarmed the rulers and authorities and put them to open shame, by triumphing over them in him." Colossians 2:13-15 ESV
I love this verse. The invisible enemy becomes visible right here. A decisive victory is won. The decisive one. When they nailed Jesus' hands and feet to that tree they also nailed the kingdom of darkness' principle weapon there also... condemnation... Christ came off the tree and lives... condemnation never did... those papers are pierced and blood stained... ruined forever.
"For though we walk in the flesh, we do not war according to the flesh. For the weapons of our warfare are not carnal but mighty in God for pulling down strongholds, casting down arguments and every high thing that exalts itself against the knowledge of God, bringing every thought into captivity to the obedience of Christ" 2 Corinthians 10:3-5 NKJV
Yes. Every thought that is raised up to obscure or contradict the knowledge of God is a thought that must be cast down. Every thought that contradicts what Christ has accomplished should have a boot firmly planted on it's neck pinning it to the ground where it belongs. Simple really... if we see what needs to be done.
The first step in warfare is to discern that an attack it is happening.
"Then I heard a loud voice saying in heaven, 'Now salvation, and strength, and the kingdom of our God, and the power of His Christ have come, for the accuser of our brethren, who accused them before our God day and night, has been cast down. And they overcame him by the blood of the Lamb and by the word of their testimony, and they did not love their lives to the death.' " Revelation 12:10-11 NKJV
The war is over. We see the future victory here in the book of Revelation. A mighty dark tree falls and crashes to the ground. Hell will be the final destination for these false rulers and authorities. They have been spoiled completely at the cross.
That victory is not seen in time yet but these invisible foes leave foot prints that can be seen... condemnation. The finished work gives us night vision. Grace opens our eyes. We see those glowing foot steps a mile away. Those dirty birds need never make a nest near us or in our thinking.
How did those Revelation Saints overcome?... 'by the blood of the Lamb and by the word of their testimony, and they did not love their lives to the death'... that is our victory as well.
Sandwiched between the blood of Christ, a physical gift of grace, and selfless abandon, a result of grace, are words backed by thoughts... words that tell a victorious personal story of grace... those words have power in the context of the finished work of Christ. Those words are filled with light that dispels darkness.