The battle of old started in the Garden of Eden when the evil one attempted to elevate himself to the position of the Most High God. He twisted the Word of God that one eventful day at the garden, and questioned God's good plan for man. And as the tickling ears of the first man and woman inclined into the lies of the devil, they became forever bound into the spiritual slavery of sin and death!
God's most precious creation is forever separated from Him by the taint of sin. There can no longer be any fellowship anymore with man and the Most Holy God, for the LORD God Almighty does not and cannot tolerate sin. His anger was kindled against the filth of sin! And from that day on, man was cast out from the presence of the LORD.
With no way to return to the LORD, man became destined to live a finite life. Death crept into the picture for it was the only thing that a sinful creature deserves. Worst, the physical death wasn't the only thing a person will face in his/her life. For the Most Holy God is also a Righteous Judge and so He had to pass a final judgment upon the soul of the sinner (Hebrews 9:27). This time the punishment is forever, and this time it is final.
What the Righteous Judge had to do with a sinner before Him was to cast him/her away from His presence forever. That sinful soul must be eternally separated from the Holiness of God, away from His rest, from His Peace, from His joy, from His Light, and from His Glory. No other place is devoid of all of God's attributes but the place that was prepared for Satan and his angels--that is, Hell.
But then, God decided to send JESUS CHRIST, His One and Only Son to die on the cross in order to SAVE the enslaved soul. And when the Son of God completed His work on the cross, He died and was buried, and was RAISED AGAIN FROM THE DEAD by God the Father!
He rose from the dead bringing with Him NEW LIFE that He offers to those who believe! Death was defeated! And the Savior has given His message (John 14:6) to those who will HEAR...
"I am the WAY, the TRUTH, and the LIFE...
He who BELIEVES in ME shall not perish
but will have eternal LIFE!"
Finally, my brethren, be strong in the Lord, and in the power of his might. Put on the whole armour of God, that ye may be able to stand against the wiles of the devil. For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.
(Ephesians 6:10-12, KJV)
Believing in the finished work of the Savior takes a lot of courage and FAITH! It takes a deep sense of TRUST in HIM and who HE claims to be. One cannot rely on His work as sufficient to save unless we come to the point of believing in who He really is--the SON OF GOD who takes away the sins of the world, and who came to save those who will believe in HIM!
Thus, the battle we wage in is never against flesh and blood, but against "principalities," which in the original Greek is ἀρχάς, arché, meaning ruler and beginning..."from the beginning." The fight is against the spiritual wickedness and darkness of this world that did not want the Light of God! It was there from the beginning of time...
How do we, who are flesh, wage war with this? By simply going back to the beginning... for everything has already been WON even before the beginning of time...
Be not thou therefore ashamed of the testimony of our Lord, nor of me his prisoner: but be thou partaker of the afflictions of the gospel according to the power of God; Who hath saved us, and called us with an holy calling, not according to our works, but according to his own purpose and grace,
which was given us in Christ Jesus
before the world began...
(2 Timothy 1:8-9)