Dispensationalism is a new way of viewing Scripture, originating in the early 1800’s, popularized by J.N. Darby and C.I. Schofield, and continues to be popular through the writings of Hal Lindsey, etc. But a vision of victory in history is taught from Genesis to Revelation; a victory which Christ’s people not only are given (by the “it is finished” of the Cross), but in which they also participate as in “The God of Peace will soon crush Satan under your feet” (Romans 16:20). We follow Him who goes forth conquering His enemies (Rev. 19:11-14) until all His enemies are subdued (Heb. 10:12-13; Psalm 110:1; Rom. 16:20), and the final enemy, death, conquered (legally and effectively at the Cross by Christ “the firstfruits”) but not fully subdued until the “rapture”, the resurrection (conquered for all of God’s people - 1 Cor. 15:24-27, on the last day when no more days of earth history follow (John 6:39-40).
I am a postmillennialist! This means I believe the Kingdom of God will progress until the nations are very substantially Christianized. Yes, there will remain unsaved people. But the majority of the world’s population will be Christian (after all, this world is a wheat field, not a tare field ). I believe Paul was a postmillennialist too! His encouragement to the Corinthians, “Your labor is not in vain in the Lord” meant more than treasures stored up in heaven for faithful labors performed.