Summary: The army of God and the malevolent demons of Satan have been at war with one another since the start of history. We are on one side or the other with no chance for neutrality. Your eternity rests on whose side you will choose when the LORD declares victory at the end of the age.
Nearly a century ago there lived a minister by the name of Donald Grey Barnhouse, who served as the pastor of Tenth Presbyterian Church in Philadelphia from 1927 until his death in 1960. He led the church through the time when the mainline Presbyterians had begun to drift away from orthodox Christian doctrine and were embracing liberal teachings such as denying the Virgin Birth of Christ, the physical resurrection of Jesus, the exclusivity of Christ as the sacrifice for sin, and church order as described in the Bible. Dr. Barnhouse was determined to remain loyal to the inerrancy and sufficiency of the Scriptures, the Lordship of Christ, and to preach what the Bible taught about humanity's sinful state and the reality of an "invisible war" being fought between the armies of God and the forces of Satan for the souls of people.
Dr. Barnhouse led numerous Bible conferences around America and the world, always telling his audience to give up looking to the world for answers, to repent of their sins, and to receive salvation found only through the Lord Jesus Christ and surrender all to Him. He emphasized the importance of daily prayer, the study of the Bible, and the importance of fellowship with brethren in a church where the Scriptures were properly taught and that Jesus Christ was confessed as Lord (John 14:6; Acts 4:12; Romans 5:6-11, 8:31-39, 10:9-10; Philippians 2:5-11). He also had a weekly radio broadcast on CBS, back when the mainstream media gave airtime to preachers and speakers. He stressed that there was a wide difference in having "religion" and a real relationship with Almighty God. This teaching was the foundation for what he referred to as "the Invisible War", first described by the apostle Paul in Ephesians 6:10-18.
Before his death in November 1960 from a brain tumor, Dr. Barnhouse had completed an initial draft of a book that he entitled "The Invisible War", a Biblical and historical examination of the unseen spiritual conflict around us. The conflict began when Lucifer, the highest of the archangels of heaven, rebelled against God and wanted to take over creation. A third of the angels joined in the rebellion, but they were all thrown out of heaven and fell to the newly created Earth. The evil persuasion of Satan, known as a serpent in Genesis 3, caused the first couple, Adam and Eve to fall into sin. As a result, God cursed the serpent, punished Adam and Eve for their disobedience but also gave them the promise of redemption and the crushing defeat of the devil and his schemes (Genesis 3:15).
This was the first of numerous Biblical prophecies foretelling of a coming Redeemer who would rescue fallen humanity from the curse of sin, death, and hell and make all things new. Satan set his focus on doing everything possible to thwart God's plans and prevent this promised Seed from appearing, including attempts to wipe out God's chosen people, pollute the bloodline, and empower rulers and renegades to kill the promised "Messiah". God would continue to frustrate and prevent Satan from carrying out his nefarious schemes, finally dealing His enemy the death blow through the work and ministry of the Lord Jesus Christ, who died on the cross bearing our sins upon Himself and Who rose from the dead to affirm that His mission of redeeming fallen humanity was a success. When the Lord Jesus returns at the end of history, He will consign the devil and all who have followed him to the Lake of Fire, where they will be punished for eternity and never return to cause havoc, sin, and death in the new heaven and earth (Revelation 21, 22).
Consider what this means in terms of our life in Christ as it stands now. The Christian life is not in any way, shape, or form a misguided belief that because we are now redeemed and secure in the salvation He gives to us that we can now sit back, attend services, sing hymns, and wait for the LORD to come back. When we look at the growing godlessness and rampant wickedness in the nation and world today, it shows that people tend not to be concerned about spiritual matters or where they will go once death comes for them. The new "religion" is built not on the Bible, but on a self-designed system of "good works", "right living", kindness, obeying the law, taking care of one's family, and other deeds that they believe will keep them in good standing with whatever deity or "force" that might be out there. They go every which way but towards the direction of the cross.
The Lord Jesus expects us to be engaged in warfare against the enemy, who keeps spiritually lost people away from the message of the Gospel. We are given weapons not only to fight the dark foes of God, but He is with us and gives us both strength and wisdom through prayer and the Word. We are not to go AWOL at a time like we see now. We cannot drop our weapons and let someone else do the fighting for us. Either option is intolerable and unbecoming of a true follower of Christ. However, we have to admit sometimes that we are getting weary in well doing and reinforcements from the King's headquarters seem to be in short supply. We who have been in the fight for awhile tend to look at the new recruits and wonder if they are truly prepared to pick up their weapon and continue the assault in the name and power of the LORD. Have we sufficiently trained our replacements to see that serving Christ is a call to the sacrifice and death of self-indulgence?